Changes

Fix DeactPDPCtxAcc when UE goes PMM ENABLED but lost its PDP context

Scenario: UE activates a PDP context, then after a while goes PMM IDLE
(Iu conn is destroyed but PDP is kept).
When UE connects through Iu again, it sends eg. RAU or ServiceRequest
with pdp_status bitmask statis the active NSAPIs.
If some NSAPI (PDP context) is enabled at SGSN but doesn't show up in
the bitmask, SGSN will destroy the PDP context with GGSN
(DeletePDPContextReq) towards GGSN prior to re-creating it.
When SGSN receives the DeletePDPContextResp, it would forward a
DeactivatePDPContextReq to the UE for a PDP context which was not known
by the UE anymore, this is wrong.

With this patch, the state of the NSAPI/PDP at the UE side is tracked,
and used to know whether when the PDP gets deleted on the GGSN side then
it needs to also be deleted on the Iu side.

Change-Id: I0ccd9228d71c29248b5f510356dbfdb09565dc30
(cherry picked from commit 4ced617eb6bb6608b6fcc14f359366551e636923)