Use higher default thread suspend timeout for run tests

Increase the default for tests from 10s-50s to 500s. This is done
by adding a run-test option "--suspend-timeout" that defaults to
500000.

Example when passing a low value of 100:
test/run-test --host --suspend-timeout 100 --dev 004-ThreadStress

Results in:
dalvikvm32 F 01-22 13:33:31 12067 12118 thread_list.cc:669] Timed
out waiting for threads to suspend, waited for 100.114ms

This should fix some of the recent test flakiness.

Test: test-art-host

Change-Id: I303c4f198e560e9f38ec375e9d7a80a5e61f776e