twister: Fix gtest harness

Some platforms prefix extra logging information before the standard
[] blocks so I've added `.\*` to the regex. Also, removed the static
values so they're only referenced using 'self.' and stopped parsing
lines after the FINISHED_PATTERN is matched since some versions of
gTest also print out a test summary after and it's not useful for
the processing.

Signed-off-by: Yuval Peress <peress@google.com>