Telephony: Trim callingUid from a synthetic sms for default sms app matching.

  4ef274dc introduced functionality that would append a callingUid for any
  synthesized message.

  The behavior in KitKat was that SMSDispatcher#handleSendComplete on
  EVENT_SEND_SMS_COMPLETE would handle writing to the default sms package.
  However, with recent changes in Lollipop for carrier packages, the calling methods
  for SMSDispatcher#sendText and SMSDispatcher#sendMultiPartText write directly
  to the default sms packages outbox if the callingpackage doesn't match the default package.

  Since the synthetic sms' calling package contains the uid, it never matches the
  default sms package, and causes a scenario where two messages are written to
  the default sms package database.

Change-Id: Ia4d8a749cabc5d16094827170d2a540e0c1486dc