Don't invoke the init target when cleaning.

I'm sure there was a good reason for this at some point, but downloading
and installing all of our dependencies before wiping out the dependencies
folder seems.... silly.

Change-Id: I16f681e6aa16b3370f4377d9519e54e18c66a241
Reviewed-on: http://gerrit.dmdirc.com/3676
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager