Escape the base64 encoded key in regexp matching

The base64 encoding of ceph keys often contains the slash / character.
This interferes with the regexp matcher slashes and thus never exits
with code 0.

The fix is to use a different RE delimiter.

Change-Id: Ia262b36250ebeb833b4a125e6b1f3976f8b069cd
Closes-Bug: #1333657