Fix the usage of rc_usage. The rc_usage function takes

a list of possible keywords, not all them in a single argument.
This also fixes the issue of extra delimiter characters appearing
on the help line from rc.d scripts not setting $extra_commands.

etc/rc.subr

@@ -515,7 +515,7 @@ run_rc_command()
 	fi
 
 	if [ -z "$rc_arg" ]; then
-		rc_usage "$_keywords"
+		rc_usage $_keywords
 	fi
 
 	if [ -n "$flags" ]; then	# allow override from environment
@@ -797,7 +797,7 @@ $command $rc_flags $command_args"
 			;;
 
 		*)
-			rc_usage "$_keywords"
+			rc_usage $_keywords
 			;;
 
 		esac
@@ -805,7 +805,7 @@ $command $rc_flags $command_args"
 	done
 
 	echo 1>&2 "$0: unknown directive '$rc_arg'."
-	rc_usage "$_keywords"
+	rc_usage $_keywords
 	exit 1
 }