storagedriver/s3: Fixed a Delete noop edgecase
storagedriver/s3: Fixed a Delete noop edgecase

Delete was not working when the subpath immediately followed the given path started with an ascii lower than "/" such as dash "-" and underscore "_" and requests no files to be deleted.

(cherry picked from commit 5d8fa0ce94b68cce70237805db92cdd8d40de282)
Signed-off-by: Collin Shoop <9630196f04a576060ab1de02adc56567730c4ce8@digitalocean.com>

thaJeztah/distribution,docker/distribution,thaJeztah/distribution,docker/distribution