MFstable/10 r301801:

MFC r300836:

Quell false positives in svc_vc_create and svc_vc_create_conn with cd and xprt

Both cd and xprt will be non-NULL after their respective malloc(9) wrappers are
called (mem_alloc and svc_xprt_alloc, which calls mem_alloc) as mem_alloc
always gets called with M_WAITOK|M_ZERO today. Thus, testing for them being
non-NULL is incorrect -- it misleads Coverity and it misleads the reader.

Remove some unnecessary NULL initializations as a follow up to help solidify
the fact that these pointers will be initialized properly in sys/rpc/.. with
the interfaces the way they are currently.

CID: 1007338, 1007339, 1007340