build: fix distcheck regression introduced from ykd binding

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Reviewed-by: Angus Salkeld <asalked@redhat.com>

exec/Makefile.am

@@ -67,7 +67,7 @@ noinst_HEADERS		= apidef.h crypto.h mainconfig.h main.h \
 			  quorum.h service.h sync.h timer.h totemconfig.h \
 			  totemmrp.h totemnet.h totemudp.h totemiba.h totemrrp.h \
 			  totemudpu.h totemsrp.h util.h vsf.h schedwrk.h \
-			  evil.h syncv2.h fsm.h votequorum.h
+			  evil.h syncv2.h fsm.h votequorum.h vsf_ykd.h
 
 if BUILD_DARWIN
 libtotem_pg.so.$(SONAME): $(TOTEM_OBJS)