Moved a variable definition to the correct place, and fixed a wrongly used service type (again)

Since the services for MoveIt! are not loadable properly when loaded at the same time as their messages, they are now referred to in a different manner in code. This way, it should work without loading problems.
Merge pull request #3 from fairlight1337/master

Moved a variable definition to the correct place, and fixed a wrongly us...