Fix: UnboundLocalError: local variable 'version_type' referenced before assignment

[furushchev]

vcs validate fails if version is referred to git hash due to unbounded variable error like below.

=== <package> (git) ===
Invocation of command 'validate' on client 'git' failed: UnboundLocalError: local variable 'cmd' referenced before assignment (/usr/lib/python3/dist-packages/vcstool/clients/git.py:736)

[EWouters]

I experienced this error as well, but this doesn't correctly fix the issue. In my case with the patch (3c0d370) it will return a hash, while my repo does have a tag checked out.

It turns out my repo has multiple tags, A and B, that point to the same commit. In the repos.yaml file tag A is requested but the repo seems to report tag B is checked out.