fix the salt.utils.expr_match

here is a new method in version `2014.7.0`, and only one caller `salt.utils.expr_match(keyid, line)` in 'salt.master.check_signing_file`. 
the caller pass keyid(the minion_id) and line(read from the autosign.conf) as sequence, but the method expr_match handles them as wrong seq.
fix it, and test it in my local env
Merge pull request #18893 from rallytime/bp-18706

Backport #18706 to 2014.7