fix handling of *_COMMIT parameters in make system

[Aleksandra Fedorova]

We have several *_COMMIT parameters in our make scripts

FUELLIB_COMMIT
NAILGUN_COMMIT
ASTUTE_COMMIT
OSTF_COMMIT

But they only support branch names and don't support commit hash.
if someone specify commit hash there, build will fail with the following error:

Cloning into '<repo>'...
fatal: Remote branch <commit_hash> not found in upstream origin

We need to replace "git clone --branch <smth>" string here

https://github.com/stackforge/fuel-main/blob/2379783517e4830868f66b5fbab512eec4695679/repos.mk#L21

with something which supports both: branch name and commit hash.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/121618

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/121618
Committed: https://git.openstack.org/cgit/stackforge/fuel-main/commit/?id=eef9afebe4c9a7e8e43ef536c881aa8f7ad52cfa
Submitter: Jenkins
Branch: master

commit eef9afebe4c9a7e8e43ef536c881aa8f7ad52cfa
Author: Sergey Kulanov <email address hidden>
Date: Mon Sep 15 19:25:30 2014 +0300

    Extends COMMIT parameters with git hash in make system

    We can define the exact commit hash or branch that
    want to use for building packages from.

    Value should be defined in config.mk with format:
     REPONAME_COMMIT?=branch
      or
     REPONAME_COMMIT?=hash
    for example:
     FUELLIB_COMMIT?=stable/5.1
     FUELLIB_COMMIT?=203ef3179007cffe3236032e61ecbaf1cd20605f

    Change-Id: Ifa225003f03dfa41028abb6db0a5ac83ad22f81e
    Close-bug: #1364076