fix bug for dual extruders not working

some guy find that marlin not working good for dual extruders delta .
when type T0 or T1 to active extruder and  E0 or E1  move causing XYZ
motion . so i locales the bugs and fix it , I have dry run the fix.
Merge pull request #866 from sakunamary/Marlin_v1

fix bug for dual extruders not working