ikev2: fix crash during peer live check
ikev2: fix crash during peer live check

Fix crash when peer tries to build INFO req before key exchange which
results using NULL key pointers for crypto operations.

Type: fix

Change-Id: I20aaf1ce769e4bfb45235047c2dd38307b4e0b59
Signed-off-by: Filip Tehlar <9891019d6f5d48a43af8fb71dfec78974db6001d@cisco.com>

FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp