Move ftpusers to libexec/ftpd/

Thsi helps with pkgbase by switching to CONFS so that ftpusers will be
properly tagged as a config file.

Approved by:	will (mentor)
Differential Revision:	https://reviews.freebsd.org/D16787

etc/Makefile

@@ -56,10 +56,6 @@ BIN1+=	etc.${MACHINE_CPUARCH}/ttys
 BIN1+= amd.map
 .endif
 
-.if ${MK_FTP} != "no"
-BIN1+= ftpusers
-.endif
-
 .if ${MK_LOCATE} != "no"
 BIN1+=	${SRCTOP}/usr.bin/locate/locate/locate.rc
 .endif

libexec/ftpd/Makefile

@@ -3,6 +3,7 @@
 
 .include <src.opts.mk>
 
+CONFS=	ftpusers
 PROG=	ftpd
 MAN=	ftpd.8 ftpchroot.5
 SRCS=	ftpd.c ftpcmd.y logwtmp.c popen.c