To handle sparse image upload, new config parameters
``rbd_thin_provisioning`` and ``filesystem_thin_provisioning``
have been added in glance for rbd and filesystem backends
respectively with enabling image_conversion plugin for both
types of backends.
To make the above parameters enable, adding 'GlanceSparseUploadEnabled'
parameter in THT.
Depends-On: Ic95fa45af0f1db92d8425862c6267f466764fbbe
Depends-On: I90c8ea98a96fa57f5bf3bf0c6b2b37ec95474baf
Partially Implements: blueprint handle-sparse-image
Change-Id: I5a339e9850be3825540873736b9734178994ce21