RBD store uses common utils for reading file chunks

Prevents cases where the image_size passed to the RBD store is larger
than the actual image_file which attempts to write 0 bytes of data
causing image.write to hang indefinitely.

Fixes LP Bug #1146830

Change-Id: I56216437a212c0c802d2ed349d88b3bd0d3bb4d7
Improve unit tests for glance.api.v1 module

Add test for glance.api.v1:
* tests for glance.api.v1.filters.validator
* tests for glance api add member method
* tests for glance api replace member method
* tests for glance api delete member method
* tests for registry api image details method
* tests for registry api image delete method
* tests for registry api add/delete/update/get member methods

Fixes: bug #1152230
Change-Id: I79d06b2281ba0c9b8d10b9300fffe6cc3c69c4ee
Merge "Improve unit tests for glance.api.v1 module"
Merge "RBD store uses common utils for reading file chunks"