Remove unused variable

o keystone/common/wsgi.py:_RE_PASS
  = re.compile(r'([\'"].*?password[\'"]\s*:\s*u?[\'"]).*?([\'"])',

  This variable was removed in the following commit.

    commit d910f1ff593dbd66f5643901142f390d0de73bdc
    Author: Brant Knudson <bknudson@us.ibm.com>
    Date:   Mon Dec 16 19:49:52 2013 -0600

        Switch to oslo-incubator mask_password

Change-Id: I6236bdb34cfcddcb338bb066450f4e89c5447e24
Merge "Remove unused variable"