o NIS clients ask for "shells" map not "shells.list".

PR:		kern/86693
Submitted by:	Victor Sudakov
MFC after:	1 month

usr.sbin/ypserv/Makefile.yp

@@ -186,7 +186,6 @@ networks:  networks.byaddr networks.byname
 protocols: protocols.bynumber protocols.byname
 rpc:	   rpc.byname rpc.bynumber
 services:  services.byname
-shells:    shells.list
 passwd:    passwd.byname passwd.byuid
 group:     group.byname group.bygid
 netgrp:    netgroup
@@ -467,7 +466,7 @@ services.byname: $(SERVICES)
 	@if [ ! $(NOPUSH) ]; then $(YPPUSH) -d $(DOMAIN) $@; fi
 	@if [ ! $(NOPUSH) ]; then echo "Pushed $@ map." ; fi
 
-shells.list: $(SHELLS)
+shells: $(SHELLS)
 	@echo "Updating $@..."
 	@$(AWK) '{ if ($$1 != "" && $$1 !~ "^#.*") print $$0"\t"$$0 }' \
 		$(SHELLS) \