Allow for setting negative priority (niceness) when $foo_user is non-root.

The order in _doit must be "nice su", not "su nice", for that.
In addition, don't ignore the exit status from "cd $foo_chdir".

Reviewed by:	freebsd-rc (silence)
MFC after:	1 week

etc/rc.subr

@@ -666,12 +666,17 @@ chroot ${_user:+-u $_user }${_group:+-g $_group }${_groups:+-G $_groups }\
 $_chroot $command $rc_flags $command_args"
 			else
 				_doit="\
-${_chdir:+cd $_chdir; }\
-${_nice:+nice -n $_nice }\
+${_chdir:+cd $_chdir && }\
 $command $rc_flags $command_args"
 				if [ -n "$_user" ]; then
 				    _doit="su -m $_user -c 'sh -c \"$_doit\"'"
 				fi
+				if [ -n "$_nice" ]; then
+					if [ -z "$_user" ]; then
+						_doit="sh -c \"$_doit\""
+					fi	
+					_doit="nice -n $_nice $_doit"
+				fi
 			fi
 
 					# run the full command;