ci, build/f_repos: Minor UX improvements

ci, build/f_repos: Minor UX improvements

After Armband rework landed of top of `build/f_repos` mechanism [1],
the following minor UX improvements can also be applied to Fuel's
f_repos:
- set SHELL to "/bin/sh" (we don't use any bash-isms);
- improve "From SHA..." removal for exported patches;
- force checkout of root tag commit during clean;
- silence progress during git clone (cleaner logs);
- support git older than 1.8.4 in `make clean` (fix Armband deploy);

FIXME:
 Pass TERM as Docker env var until [2] is fixed in Docker 1.13.

v4 -> v5:
 * Moved `export TERM` to Releng, where it actually belongs [3];
 * Fixed Armband deploys fail [4] by adjusting `make clean`;

[1] https://gerrit.opnfv.org/gerrit/#/c/22791/
[2] https://github.com/docker/docker/issues/9299
[3] https://gerrit.opnfv.org/gerrit/#/c/22933/
[4] https://build.opnfv.org/ci/view/armband/job/\
    fuel-deploy-armband-baremetal-daily-master/57/consoleText

Fixes: FUEL-200

Change-Id: I80e3074f8659769e21f5b56f07c34c7a5de727bc
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>