detect_mx_short_dial: return dest num on exception
detect_mx_short_dial: return dest num on exception

We are assigning the return value from this function to
destination_number, so return the input if we catch
an Exception with the db query.

Rhizomatica/rccn,Rhizomatica/rccn,Rhizomatica/rccn,Rhizomatica/rccn,Rhizomatica/rccn