Update stage1 and stage3 to run robot tests with tag

This reverts commit b311476d

.

This commit updates stage1 and stage3 to allow running robot
tests in stage3 by default for every commit.

The commit removes param DO_STAGE_4 since it is confusing. Only
params DO_ROBOT and ROBOT_TAG_NAME will be used. If DO_ROBOT is set
to true, robot tests will be run in stage3 for all tests containing
the tag indicated by ROBOT_TAG_NAME. The param ROBOT_TAG_NAME replaces
the previous param TEST_NAME.

MDG stage1 can specify params DO_ROBOT and ROBOT_TAG_NAME. If
specified, they will be used. Otherwise, the default for stage3 will
apply (DO_ROBOT=true, ROBOT_TAG_NAME=sanity).

Daily job, which will run stage1, can also specify params DO_ROBOT
and ROBOT_TAG_NAME. In principle, they will be set as follows:
DO_ROBOT=true, ROBOT_TAG_NAME=daily.

Stage1 job, in case of failure, will send an e-mail to OSM_MDL
mailing list reporting the failure. The mail will only be sent
if the name of the job starts with "daily-stage_4".

Change-Id: Ibe37fb588fc48297f5fea6e654f9ad64c906d9a6
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>