TeleService : Add networkmode changed listener

GSM option screen also has networkmode select list when
isLteOnCdma is true, but there is no preference change
listener.

Add preference change listener for it.

CRs-Fixed: 746647

Change-Id: Ic3b914d93c8507307bbfa940d4546ee0deceae08
TeleService: Add hold capability to CdmaConnection

When create CdmaConnection, the hold capability is
not added.

Add hold capability to the CdmaConnection.

Change-Id: I5dc3a62941b044b174e8997cabfef381121b7486
CRs-Fixed: 742911