test_query_profile_thrift_timestamps causes following tests to fail

test_query_profile_thrift_timestamps calls "self.client.close()". This is not really a valid thing for a test to do, as "self.client" is opened in setup_class and expected to remain valid for all of the tests in a suite until teardown_class is called, and so any tests following it in the class that rely on "self.client" will not work.

This hasn't been a problem in builds yet as test_query_profile_thrift_timestamps is marked "serial", there are no other "serial" tests following it in the suite, and tests are normally run via "tests/run-test.py", which runs the parallel and serial tests separately.

I only hit this because I was running tests via "bin/impala-py.test" which, without any args, runs all tests serially, but we should still fix it.