Handle source PDN lost during HO

when source PDN is reported lost duing HO, source transport thinks the old interfaceName can be reused
by other PDN, but because HO in progress, the current network is still under the old interfaceName. Fix by mark current network SUSPENDED
 and update the current interfaceName to be "" .

Test: atest + basic placing phone call
Fix: 243698950
Change-Id: I7650c79ba1a9a69a22f6a0e67cf7932f6fa2dfc3