Unify the shell to bash in all Kolla scripts.

Change-Id: Ib9591b2f8f344eb88455c5e9b7ecf2164fb5960a
Implements: blueprint use-bash-shell

YAML files can have .yaml or .yml extension. Make `validate-all-yaml.sh`
check for *.yml files in addition to *.yaml files since we now have some
of these in our source tree.

This should help to prevent bogus YAML files to land in the repository.

Change-Id: Id59273680fc2424f7b636033b1d641efcaaeba22

Remove git and jq dependency in most scripts, allowing to run them on
latest atomic images, or even distribute Kolla in the form of tarball.

The only remainings of git dependency are in the git pre-commit hook,
and in the image build scripts. We can remove the latter one and have
the scripts running in degraded mode if we really want to.

I opted for a python based approach to finding the top-level directory
for portability, ensuring consistent result on Linux and BSD, including
OSX.

Change-Id: I987174032d11b2e9d6a993c563b5dc877c15dd2d

This patch adds a script for validating YAML files, and replaces the
existing JSON checks with one largely identical to the YAML check.

This also provides a script that can be installed as a pre-commit hook
that will perform this checks when you commit changes.  You can install
the hook by running tools/pre-commit-hook --install.

Change-Id: Ib4742a9db062362cfa61d669c691151bc1ca376c