Drop infinite loops in favor of finite wait_for

Drop infinite loops in favor of finite wait_for

While at it, fix some shellcheck warnings, and s/fgrep/grep -F/g.

Change-Id: I093b7b4c196731b1ecc0c27a4111955b2e412762
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
(cherry picked from commit 089585ad5370109d4c2a476b94b0017153d7713d)