Fixed an inverted race condition when installing with MAKEOPTS="-j1"

jer found this:
  install-root_sbinPROGRAMS is called from install-data-am but
  install-exec-hook is called from install-exec-am

So moving the failing ln call into install-data-hook for now...

--- cifs-utils-6.12/Makefile.am
+++ cifs-utils-6.12/Makefile.am
@@ -117,10 +117,8 @@
 
 SUBDIRS = contrib
 
-install-exec-hook: install-sbinPROGRAMS
+install-data-hook: install-sbinPROGRAMS
 	(cd $(DESTDIR)$(ROOTSBINDIR) && ln -sf mount.cifs mount.smb3)
-
-install-data-hook:
 if CONFIG_MAN
 	( cd $(DESTDIR)$(man8dir) && ln -sf mount.cifs.8 mount.smb3.8)
 endif