Fix NewInstanceString test to not time out getting string value.

Checks the string value while the debuggee is still suspended on a
breakpoint.

Bug: 30951794
Cherry-pick of two changes:
ea4486cd693527acfcc5aa85a2faebf969142242
93c6e5c49ebaa5e4c6630b21dac49df52143f54c

Change-Id: I9218cec067e6a7ad39fd83680f82aeae0374e3e0
3 files changed