gating.yaml: Fix TestInstallMaster timeout
    
    test_integration/test_installation.py::TestInstallMaster 's
    timeout is 10800 on all nightlies but it timeouts in gating with a
    timeout of 3600. Use 7200 in gating so that it has some chance of
    completing.
    
    Signed-off-by: François Cami <fcami@redhat.com>
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>
    Reviewed-By: Stanislav Levin <slev@altlinux.org>