Avoid special characters in ceilometer passwords

Fixes a problem when the auto-generated password contains a colon:
2014-04-11 05:42:18.175 12757 CRITICAL ceilometer [-] ':' or '@' characters in a username or password must be escaped according to RFC 2396.
Merge pull request #22 from cdwertmann/patch-4

Avoid special characters in ceilometer passwords