build/f_repos: Fix remote tracking, pin N HEADs

Fix two issues that went undetected until now:
- remote tracking variable does not properly evaluate in CI,
  since there is no HEAD reference;
- git submodules references still point to master branch(es)
  commits, although .gitmodules configure the remote tracked
  branch correctly;

JIRA: FUEL-234

Change-Id: I96dc704e2cfe98f2e93d5fa7d7dd261e7f151238
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

1 files changed, 0 insertions, 0 deletions

diff --git a/build/f_repos/sub/fuel-nailgun-agent b/build/f_repos/sub/fuel-nailgun-agent
-Subproject af1e5da094c2975230da29f808b26645231841d
+Subproject 0cfe06be939f92c3a8158a0e8a96a7ab8cf5403