Bug 1333264 - Only skip test_master_password.html on platforms with failures.

Differential Revision: https://phabricator.services.mozilla.com/D20324

--HG--
extra : moz-landing-system : lando

toolkit/components/passwordmgr/test/mochitest/mochitest.ini

@@ -76,7 +76,7 @@ skip-if = toolkit == 'android' && debug # bug 1397615
 [test_input_events_for_identical_values.html]
 [test_master_password.html]
 scheme = https
-skip-if = true #bug 1333264
+skip-if = os != 'mac' # Tests desktop prompts and bug 1333264
 support-files =
   chrome_timeout.js
   subtst_master_pass.html