Revert "Disable eventlet monkey-patching of DNS"

This reverts commit 6219f94b3a1103a16bd5f16ed8ffdd41a85280e1.

This commit seems to cause keystone auth to hang when using
Keystone w/ Swift.

Fixes LP Bug #1178646.

Change-Id: Ieb94a29b3129847c84a02c8a526611f125f21ea0
Allow backend & client SQL tests on mysql and pg.

Currently the tables are not created which means that it isn't
possible for these tests to run on anything other than sqlite.

Fix test issues where the token id that is used to create the token is
not the same as the id that the token is saved with.

Fix a number of foreign key constraints issues.

Bug  1178041

Change-Id: Ib67eb97836e4224940abdeae4bba66748bfe4ca5