Include call to delete_subnet from delete_network at DB level

Removes an extra lock in bsn plugin that causes a deadlock
when delete_subnet is invoked form delete_network, agreed
with kevinbenton to remove it
Modifies a unit test to cover this change per reviewer request
Co-author amirosh

Closes-bug: #1197176

Change-Id: Ie3414848a91cc737b16b79399ae19800545e533f
Cleanup and refactor methods in unit/test_security_groups_rpc

We had strings repeating all along the code which already were
in constant form, those have been refactored. Also global configuration
changes are now handled by functions to enhance code readability.

Change-Id: I0d4e508cda2537abe431f04a278ba2e1d2f5d97d
Update i18n translation for neutron.db log msg's

Validate that hacking rules apply to directory neutron/db
Partial-bug: #1320867

Change-Id: Iffdaa28bf5d5d503623f1f6dec4a8003f48974d8
Update i18n translation for neutron.extension log msg's

Validate that hacking rules apply to directory neutron/extensions

Change-Id: Ifbc97ae2b5670fbdf22c7d0ae48f91a7776daf01
Partial-bug: #1320867
Merge "Include call to delete_subnet from delete_network at DB level"
Merge "Update i18n translation for neutron.db log msg's"
Merge "Update i18n translation for neutron.extension log msg's"
Merge "Cleanup and refactor methods in unit/test_security_groups_rpc"