test: pass flags to services

test: pass flags to services

Commit 4c12714d1ca0 ("test: run tests on system level mdadm") removed
MDADM_NO_SYSTEMCTL flag from test suite. This causes imsm tests to fail
as mdadm no longer triggers mdmon and flags exists only within session.

Use systemd set/unset-environment to pass necessary flags.

Introduce colors to grab users attention to warnings and key messages.

Make test suite setup systemd environment.
Add setup/clean_systemd_env() functions.
Warn user about altering systemd environment.

Add colors to success/fail messages and warnings.

Signed-off-by: Mateusz Kusiak <mateusz.kusiak@intel.com>