RFR(S/M): 8195809: [TESTBUG] jps and jcmd -l support for containers is not tested

[mikhailo.seledtsov at oracle.com]

Please review this new test for JCMD across container boundary.
It also updates DockerTestUtils:
   - buildJdkDockerImage now accepts additional Dockerfile content
   - new method to kill a container

     JBS: https://bugs.openjdk.java.net/browse/JDK-8195809
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8195809.01/
     Testing:
         1. Ran the new test on Linux-x64: PASS
         2. Ran all hotspot and JDK container tests on Linux-x64:
            test/hotspot/jtreg/containers/docker 
test/jdk/jdk/internal/platform/docker/
            All PASS

Thank you,
Misha