Fix syntax errors (s/:=/:-/).

Reviewed by:	emaste (mentor)
Approved by:	emaste (mentor)
MFC after:	3 days

etc/rc.d/bgfsck

@@ -17,7 +17,7 @@ stop_cmd=":"
 bgfsck_start()
 {
 	if [ -z "${rc_force}" ]; then
-		background_fsck_delay=${background_fsck_delay:=0}
+		background_fsck_delay=${background_fsck_delay:-0}
 	else
 		background_fsck_delay=0
 	fi

etc/rc.d/named

@@ -173,7 +173,7 @@ named_prestart()
 		warn 'named_pidfile: now determined from the conf file'
 	fi
 
-	command_args="-u ${named_uid:=root}"
+	command_args="-u ${named_uid:-root}"
 
 	if [ ! "$named_conf" = '/etc/namedb/named.conf' ]; then
 		case "$named_flags" in