Fix [#37085] Hook modifier work when created with Ctrl+H, but not when created via modifier panel

"transform matrix" of the hook was not inited (reset) when assinging and object to it, now use same code for both OBJECT_OT_hook_reset operator and RNA object assignement.

Reviewed by Brecht, thanks.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60777 954f8c5b-7b00-dc11-b283-0030488c597c