Additional tests in jmxremote/startstop to match on PID not app name

Since
8207908: JMXStatusTest.java fails assertion intermittently

which updates:
test/jdk/sun/management/jmxremote/startstop/JMXStatusTest.java
test/jdk/sun/management/jmxremote/startstop/ManagementAgentJcmd.java

the related tests:
test/jdk/sun/management/jmxremote/startstop/JMXStartStopTest.java
test/sun/management/jmxremote/startstop/JMXStatusPerfCountersTest.java

...fail to compile:

test/jdk/sun/management/jmxremote/startstop/JMXStartStopTest.java:75: error: incompatible types: String cannot be converted to Process
    private static ManagementAgentJcmd jcmd = new ManagementAgentJcmd(TEST_APP_NAME, verbose);


These tests also use jcmd using an application name pattern and presume they see output from the program they started, and not some other concurrent test invocation.