Rebase when uploading release because we have been using dev releases
Don't mask real failure to upload stemcell/release

We were originally ignoring failures to avoid failing when re-uploading
the same stemcell. This should be a rare occurrence during development
only.
Add 'require' needed to use director by itself.

[52819141]

Signed-off-by: Tony Hansmann <thansmann@pivotallabs.com>