RFR(M): 8172970: TESTBUG: need test coverage for the JVMTI functions allowed in the start phase

[serguei.spitsyn at oracle.com]

Please, review the jdk 10 fix for the test enhancement:
   https://bugs.openjdk.java.net/browse/JDK-8172970


Webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2017/hotspot/8172970-start-phase.1/


Summary:
   The task was to provide a test coverage for the JVMTI functions 
allowed during the start phase.
   It includes both enabling and disabling the 
can_generate_early_vmstart capability.
   Testing the JVMTI functions allowed in any case has not been targeted 
by this fix.

Testing:
   New test is passed.


Thanks,
Serguei