ch3: Fix uninitialized bytes caused by MPIDI_Pkt_init

In meminit debug mode, we need to initialize all packet headers before
sending them. Since ch3 uses a fixed header size, we need to make sure
to initialize the whole header and not just the subtype used for a
particular message.

Author: raffenet

src/mpid/ch3/include/mpidimpl.h

@@ -464,7 +464,7 @@ void MPIDI_DBG_PrintVCState(MPIDI_VC_t *vc);
 #else
 #   define MPIDI_Pkt_init(pkt_, type_)				\
     {								\
-	memset((void *) (pkt_), 0xfc, sizeof(*(pkt_)));	\
+	memset((void *) (pkt_), 0xfc, sizeof(MPIDI_CH3_Pkt_t));	\
 	(pkt_)->type = (type_);					\
     }
 #endif