Make bash code to upload images a bit more solid

Fail earlier if there's an issue.
Avoid hard-coding of cirros version
Reorder searches for openstack components
Do not respect the use_gitrepo setting for installing clients

This makes no sense: we know the stable clients are working anyway with
glance/nova from git.
Install clients for all openstack components

We use some of them in the config recipe, and anyway, tempest is testing
the CLI tools.
Always run neutron tests in tempest

We require neutron to be installed to have nova installed, so we know
it's always there.
Look if there's an endpoint to know if something should be tested
Reorganize order of variables for tempest.conf template

No functional change, but more readable.
Add FIXME for searches that do not have a fully correct query

We always need to search with an environment...
Remove use of .venv/bin/activate for CLI tools

Since the tools are always installed from packages, this is not required
anymore.
Always use "/usr/bin" as directory for the CLI tools in tempest config

We always install them from packages.

It's worth mentioning that scripts like tempest_cleanup.sh that we
generate assume this also.
Use find_dep_proposal helper on proposal creation
Update tempest_smoketest.sh to use the right command for running tempest
Remove unneeded temporary variables in generated scripts
Define environment variables in tempest_smoketest.sh only in subscript

We don't need them elsewhere.