[ZOOKEEPER-3642] Fix potential data inconsistency due to DIFF sync after partial SNAP sync.

[hanm]

Based on #1224 ; fixed unit test build issue.

[eolivelli]

LGTM

[eolivelli]

I have restarted manually the CI job
https://ci-hadoop.apache.org/blue/organizations/jenkins/zookeeper-precommit-github-pr/detail/PR-1515/2/pipeline

[hanm]

I have restarted manually the CI job
https://ci-hadoop.apache.org/blue/organizations/jenkins/zookeeper-precommit-github-pr/detail/PR-1515/2/pipeline

I tried multiple times and can't get a green CI build. All JVM tests pass, and the build failed at C client build step:
`[2020-10-26T14:14:15.576Z] autoreconf: cannot create /tmp/user/910/ar4585.2200: No such file or directory

[2020-10-26T14:14:15.576Z] at /usr/bin/autoreconf line 691.

[2020-10-26T14:14:15.576Z] [ERROR] Command execution failed.

[2020-10-26T14:14:15.576Z] org.apache.commons.exec.ExecuteException: Process exited with an error: 2 (Exit value: 2)

[2020-10-26T14:14:15.576Z] at org.apache.commons.exec.DefaultExecutor.executeInternal (DefaultExecutor.java:404)

[2020-10-26T14:14:15.576Z] at org.apache.commons.exec.DefaultExecutor.execute (DefaultExecutor.java:166)

[2020-10-26T14:14:15.576Z] at org.codehaus.mojo.exec.ExecMojo.executeCommandLine (ExecMojo.java:804)

[2020-10-26T14:14:15.576Z] at org.codehaus.mojo.exec.ExecMojo.executeCommandLine (ExecMojo.java:751)

[2020-10-26T14:14:15.576Z] at org.codehaus.mojo.exec.ExecMojo.execute (ExecMojo.java:313)

[2020-10-26T14:14:15.576Z] at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)

[2020-10-26T14:14:15.576Z] at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)

[2020-10-26T14:14:15.576Z] at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)

[2020-10-26T14:14:15.576Z] at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)

[2020-10-26T14:14:15.576Z] at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)

[2020-10-26T14:14:15.576Z] at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)

[2020-10-26T14:14:15.576Z] at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)

[2020-10-26T14:14:15.576Z] at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)

[2020-10-26T14:14:15.576Z] at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)

[2020-10-26T14:14:15.576Z] at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)

[2020-10-26T14:14:15.576Z] at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)

[2020-10-26T14:14:15.576Z] at java.lang.reflect.Method.invoke (Method.java:498)

[2020-10-26T14:14:15.576Z] at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)

[2020-10-26T14:14:15.576Z] at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)

[2020-10-26T14:14:15.576Z] at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)

[2020-10-26T14:14:15.576Z] at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)

[2020-10-26T14:14:15.576Z] [INFO] ------------------------------------------------------------------------`

Not exactly sure what went wrong ... this patch is not supposed to impact C client build (or test)..

[hanm]

@eolivelli this is ready to merge now we finally get a green build.

[ztzg]

@hanm, @eolivelli: Should I take care of this?

[eolivelli]

thank you @ztzg for the remained. I have merged the patch.

The original author was @lvfangmin
I have set @hanm and added a reference to @lvfangmin in the commit message.

[ztzg]

@eolivelli: I did not mean to push you. But, LGTM :)