kern: malloc: fix panic on M_WAITOK during THREAD_NO_SLEEPING()

Simple condition flip; we wanted to panic here after epoch_trace_list().

Reviewed by:	glebius, markj
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D29125

sys/kern/kern_malloc.c

@@ -537,7 +537,7 @@ malloc_dbg(caddr_t *vap, size_t *sizep, struct malloc_type *mtp,
 #ifdef EPOCH_TRACE
 			epoch_trace_list(curthread);
 #endif
-			KASSERT(1, 
+			KASSERT(0,
 			    ("malloc(M_WAITOK) with sleeping prohibited"));
 		}
 	}