chan_sip: Don't ignore expires value in contact header if it lacks semicolon

(closes issue ASTERISK-22574)
Reported by: Filip Jenicek
Patches:
    chan_sip_expires.patch uploaded by Filip Jenicek (license 6277)


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@400469 f38db490-d61c-443f-a65b-d21fe96a405b