Removing .pants.d during clean.sh makes it easier for me to get past the Untranslatable... exception

Testing Done:
travis-ci passes.

Tested manually

~/Src/Pants zundel/remove-dot-pants-dot-d ls .pants.d/
build_invalidator compile           gen               ivy               ng                python            reports           resources         runs              test              thrift
~/Src/Pants zundel/remove-dot-pants-dot-d ./build-support/python/clean.sh
~/Src/Pants zundel/remove-dot-pants-dot-d ls .pants.d/
ls: .pants.d/: No such file or directory

Bugs closed: 210

Reviewed at https://rbcommons.com/s/twitter/r/500/