rib: Update to properly handle optional ExpirationPeriod in RibRegister command

Change-Id: I9f18988f295a993e53dc03547f2f20967431dc10
Refs: #1772
rib: Fixing bug with RibUnregister when route origin is not specified

Change-Id: Ica250a1c45ed42f1dc7862a12916f893fa846312
Refs: #1773