Use environemnt variable for tuxSuite

To ensure jenkins jobs can run on both OpenCI
and Arm CI, replace harcoded variables with
enironment variable.

These are system-wide environment variable and
are configured in:
Manage Jenkins > System > Global Properties

Change-Id: Icd8de032d02b08b1e9d45926ae063654a47bf72b
Signed-off-by: Saheer Babu <saheer.babu@arm.com>
3 files changed