RFR(XXS) 8212877: Restore JTREG_VERBOSE value for mach5 testing

[Ekaterina Pavlova]

Hi All,

Please review this extra small change which restores JTREG_VERBOSE value for mach5 testing.

Default JTREG_VERBOSE value was changed from "fail,error,time" to "fail,error,summary" after switching to run-test framework (JDK-8212028).
Having compact tests output is good for local users while mach5 testing will benefits from providing more test execution information.
Specially having test time execution data helps to analyze any tests/jobs slowness.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8212877
  webrev: http://cr.openjdk.java.net/~epavlova//8212877/webrev.00/index.html
testing: tested by launching jobs in Mach5

thanks,
-katya