Allow sequential installation of ONOS in STC
Allow sequential installation of ONOS in STC

- Check for ONOS_STC_SEQ_START env variable, and if set, install ONOS in
  sequence instead of in parallel

Change-Id: I6c5d9d2e46293ec3c02b1de22227d3a81d48a45f

oplinkoms/onos,oplinkoms/onos,sdnwiselab/onos,kuujo/onos,oplinkoms/onos,oplinkoms/onos,osinstom/onos,LorenzReinhart/ONOSnew,gkatsikas/onos,LorenzReinhart/ONOSnew,sdnwiselab/onos,osinstom/onos,oplinkoms/onos,gkatsikas/onos,kuujo/onos,opennetworkinglab/onos,opennetworkinglab/onos,gkatsikas/onos,sdnwiselab/onos,sdnwiselab/onos,kuujo/onos,kuujo/onos,oplinkoms/onos,opennetworkinglab/onos,sdnwiselab/onos,opennetworkinglab/onos,osinstom/onos,gkatsikas/onos,LorenzReinhart/ONOSnew,kuujo/onos,opennetworkinglab/onos,LorenzReinhart/ONOSnew,opennetworkinglab/onos,LorenzReinhart/ONOSnew,kuujo/onos,gkatsikas/onos,osinstom/onos,oplinkoms/onos,sdnwiselab/onos,kuujo/onos,osinstom/onos,gkatsikas/onos