RFR(XS): 8072401, 8072403, 8072405: Small fixes to newly added DCMD tests

[Mikael Auno]

Hi, could I please have some reviews for these very small fixes.

Webrev:
http://cr.openjdk.java.net/~miauno/8072401_8072403_8072405/webrev.00/

Issues:

Some of the newly added DCMD tests fail due to lack of -XX:+UsePerfData
https://bugs.openjdk.java.net/browse/JDK-8072401

HeapDumpTest and HeapDumpAllTest fails to find jhat in non-JDK runs
https://bugs.openjdk.java.net/browse/JDK-8072403

DCMD tests needs at least compact3 profile
https://bugs.openjdk.java.net/browse/JDK-8072405

Thanks,
Mikael