Fixed crash issues in AT+KHTTP commands
Fixed crash issues in AT+KHTTP commands

Fixed two crash issues in AT+KHTTP commands
1: In HttpClientStateMachine(), re-check the http client reference after
eventCb(), and just return if the reference is freed.
2: In processHttpFinalResult(), do not switch to AT mode if current http
client session is not in DATA mode.

Resolves: LE-14596
Cherry-pick: QTI9X07TX-1747
Change-Id: Ia4e3b334667dba621e786df04abdf5bde44361fb
Signed-off-by: azhao <cd00864fdac84f146b25dd04743df78b001d11d4@sierrawireless.com>

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af