docker info: fix connection errors and exit code being discarded

[thaJeztah]

Check whether formatInfo or prettyPrintInfo handled the error, otherwise return it. Previously we'd print the error, but the function may not have handled the error if a template was used that didn't consume the ServerErrors field.

Before;

docker -H example.invalid info > /dev/null
ERROR: error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host
errors pretty printing info
echo $?
1

docker -H example.invalid info --format '{{.Architecture}}' > /dev/null
error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host

echo $?
0

# invalid template
docker -H example.invalid info --format '{{.Whoops}}' > /dev/null
error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host
template: :1:2: executing "" at <.Whoops>: cant evaluate field Whoops in type system.dockerInfo
echo $?
1

After;

docker -H example.invalid info > /dev/null
ERROR: error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host
errors pretty printing info

echo $?
1

docker -H example.invalid info --format '{{.Architecture}}' > /dev/null
error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host

echo $?
1

docker -H example.invalid info --format '{{.Whoops}}' > /dev/null
error during connect: Get "http://example.invalid:2375/v1.48/info": dial tcp: lookup example.invalid: no such host
template: :1:2: executing "" at <.Whoops>: cant evaluate field Whoops in type system.dockerInfo

echo %?
1

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