MMS: Fix lookup of vanity addresses

Avoid the use of the function PhoneNumberUtils.stripSeparators for non-strict
phone numbers.

Change-Id: I9750b86a0a909f5436b4fc0717414c6a9bbdd794
JIRA: CYAN-57
Issue: https://jira.cyanogenmod.org/browse/CYAN-57
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>