Because we were passing query strings as symbols, the fog-aws storage
driver was omitting the uploadId and partNumber query strings
from the signature in multipart uploads. This fix makes AWS and Ceph work with
v2 signatures.

See: https://github.com/fog/fog-aws/blob/v3.0.0/lib/fog/aws/storage.rb#L733

Closes https://gitlab.com/gitlab-org/gitlab-workhorse/issues/181