make engine api handle string or bool disable_rollback

Allow API's to pass string or bool format True/False flag
for the disable_rollback argument to the engine RPC API

Change-Id: I1886263ac2487c4cb36c8bd93fd1d09b04abe813
heat api : Handle DisableRollback parameter in cfn API

Previously we ignored DisableRollback for create/update,
pass it to the engine since the engine API now supports it

blueprint stack-rollback

Change-Id: I926d843a88449fa61b665bd1b47946724f6d2ce5
heat tests : delete stacks from DB in parser tests

The tests which store a stack in the DB should delete it
at the end of the test, otherwise any cut/paste test
which uses the same stack name will always fail

Change-Id: Ib2e26480924bfe65a2f6fe8ae55076466394bcee
heat cli : Add --disable-rollback option to heat-cfn

When rollback is implemented it will default on, like aws
so this option allows stack rollback on create to be disabled

blueprint stack-rollback

Change-Id: I02fcaaa656219b1c65729cecdd473e0a5bd86036
Provide unit test coverage for AWS::EC2::SecurityGroup

There were some issues that testing revealed, includes fixes
for those.

Fixes bug 1129577

Change-Id: I31b02c7fc9179b61b74dd18a38e15d126b406f80
Merge "Provide unit test coverage for AWS::EC2::SecurityGroup"