Fixed quotes in _assert_tables() method

We suppose, that for some reason we need double-quotes around the
some table names (see change id Id93283905256247bdd2663b799d41a7925804542)
but there is also can be normal case, when we have table names without quotes

Related to blueprint db-use-oslo-common-code

Change-Id: I834cafc6796d517d731c3324fff5008c08b31f7a
Adds domain level support for tasks

Includes:-
  - Domain Task class
  - Domain TaskFactory class
  - DB TaskRepo class
  - Necessary proxy classes for all of the above
  - Tasks related exceptions
  - Unit tests as applicable

Partially implement blueprint async-glance-workers

Change-Id: I619224bcc55b62303f3539454649528f2edc6e9d
Merge "Adds domain level support for tasks"
Merge "Fixed quotes in _assert_tables() method"