g-api raises 500 error while uploading image

If both filesystem_store_datadirs and filesystem_store_datadir parameters
specified in glance-api.conf file then while creating new image 500
internal server error is raised.

Caught StoreAddDisabled exception for v1 and v2 api while uploading
image and raised HTTPGone exception to return HTTP 410 response to
user.

Closes-Bug: #1372888
Change-Id: Iccbf5b88634d3c956d41e8d8a0126648c64b34eb
Merge "g-api raises 500 error while uploading image" into proposed/juno