RFR(S): 8228960: [TESTBUG] containers/docker/TestJcmdWithSideCar.java: jcmd reports main class as 'Unknown'

[mikhailo.seledtsov at oracle.com]

Please review this change that fixes a container test TestJcmdWithSideCar.

My investigation indicated that a root cause for this failure is:
JCMD -l shows 'Unknown' for class name because the main class has not 
been loaded yet.
The target test JVM has started, it is initializing, but has not loaded 
the main test class.

The proposed solution is to try 'jcmd -l' several times, with a short 
sleep in between.

Also I have commented out the testCase02() due to another bug:
"JDK-8228850: jhsdb jinfo fails with ClassCastException: 
s.j.h.oops.TypeArray cannot be cast to s.j.h.oops.Instance",
which is not a test bug. IMO, it is better to run the test and skip a 
sub-case than to skip the entire test.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8228960
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8228960.00/
     Testing:
         1. Locally: ran test 50 times on Linux-x64
         2. Test Cluster: ran several dozen times on a variety of 
Linux-x64 host, including
            the hosts where the original failure was detected.


Thank you,
Misha