[tests] Use the TestCA context in all the manager tests in manager_test.go

[cyli]

So that the test names are displayed in the test output. This was useful for debugging manage test failures.

[codecov]

Codecov Report

Merging #2269 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2269      +/-   ##
==========================================
- Coverage   60.36%   60.34%   -0.02%     
==========================================
  Files         125      125              
  Lines       20394    20394              
==========================================
- Hits        12311    12307       -4     
+ Misses       6694     6690       -4     
- Partials     1389     1397       +8

[aaronlehmann]

LGTM

As a random aside, when I was making the changes that caused the tests to run on a ram disk in CI, I noticed that my test runs were leaving behind temporary directories. My first suspicion was that we were forgetting some RemoveAll calls, but at least in the case of competing-ca-server, this doesn't seem to be the case. My next thought was that we were calling RemoveAll while files were still in use, and the call was failing. However, I spent some time adding assertions to many of the RemoveAll calls in the test code, and didn't see any fail, so figured that probably wasn't the problem.

It may be that in some tests, the directories get recreated after RemoveAll finishes.

I can reproduce the leakage locally, and I see a directory from competing-ca-server, several from swarm-ca-test, two from test-raft, and two from test-socket.

[cyli]

@aaronlehmann Thanks, I'll see if I can figure out what's causing those