Bug 857599 - Clone profile for Marionette tests to prevent polluting the original profile. r=jgriffin, a=test-only

--HG--
extra : amend_source : 152b4cb30275e22798280fe88a19b473ddd74451
extra : transplant_source : %F9%D3%E8%CC%84%17%84%1E%8C%10j%F4%026%A1b%3E%896%12