[autotest] add ssh_verbosity to test_that and autoserv_utils

BUG=chromium:271621
TEST=unit tests pass. Manually verified that flag works as expected.

Change-Id: I31c59a80a7a2151c27d4a41ff8c6cfbf51d259cb
Reviewed-on: https://gerrit.chromium.org/gerrit/65720
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
3 files changed