Check --store parameter validity before _reserve

Currently the value of the --store parameter is checked after the call
to _reserve is made. Thus the image is actually created on the
database even though the store is invalid, and then returns a E400.

Change-Id: Ic27ed30e605794342161530e8a8eacd6e6deb5d9
Closes-bug: #1260314
Use common db migrations module from Oslo

Changes due to use common migration module instead of Glance
implementation.
Removed glance.db.sqlalchemy.migration module and related code.

blueprint db-use-oslo-common-code

Change-Id: Ib7e2e478a84a90cc9c773f2733dc60b88834fd23
Merge "Check --store parameter validity before _reserve"