[autotest] Wait for ownership during CryptohomeMounted test

if we dont wait for ownership to complete after login, then we can
wind up sigabrting the tool that takes ownership, leading to test
failures.

BUG=12616
TEST=suite_Smoke
STATUS=Fixed

Change-Id: I5d22fb1e8571bec8a78297fa894861b7591e635d

Review URL: http://codereview.chromium.org/6602035
1 file changed