Ignore false positive Bandit test

Improvements[1] to the B105 hardcoded_password_string[2] test in Bandit
result in it now catching a false positive. Add a # nosec comment to
skip Bandit testing of that line.

[1] https://github.com/PyCQA/bandit/issues/386
[2] https://bandit.readthedocs.io/en/latest/plugins/b105_hardcoded_password_string.html

Change-Id: I822526a7dbdd9be51edefaf6b24011fcce6e4121

heat/common/context.py

@@ -46,7 +46,7 @@ LOG = logging.getLogger(__name__)
 # username = heat
 # password = password
 # user_domain_id = default
-PASSWORD_PLUGIN = 'password'
+PASSWORD_PLUGIN = 'password'  # nosec Bandit B105
 TRUSTEE_CONF_GROUP = 'trustee'
 ks_loading.register_auth_conf_options(cfg.CONF, TRUSTEE_CONF_GROUP)