Add wait for connection to restore after l3 agent migration
Add wait for connection to restore after l3 agent migration

- After l3 agent rescheduling connectivity is restoring for some
period of time so we need to wait a few minutes before checking
connectivity on instance

Change-Id: Iafbf677bb902d64ae7e33346f2701900e30c9342
Closes-Bug: #1401819

dancn/fuel-main-dev,teselkin/fuel-main,SergK/fuel-main,teselkin/fuel-main,SergK/fuel-main,Fiware/ops.Fuel-main-dev,Fiware/ops.Fuel-main-dev,ddepaoli3/fuel-main-dev,zhaochao/fuel-main,SmartInfrastructures/fuel-main-dev,eayunstack/fuel-main,ddepaoli3/fuel-main-dev,eayunstack/fuel-main,huntxu/fuel-main,ddepaoli3/fuel-main-dev,AnselZhangGit/fuel-main,teselkin/fuel-main,SergK/fuel-main,huntxu/fuel-main,zhaochao/fuel-main,stackforge/fuel-main,Fiware/ops.Fuel-main-dev,zhaochao/fuel-main,AnselZhangGit/fuel-main,eayunstack/fuel-main,SmartInfrastructures/fuel-main-dev,dancn/fuel-main-dev,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-main,AnselZhangGit/fuel-main,teselkin/fuel-main,dancn/fuel-main-dev,SmartInfrastructures/fuel-main-dev,zhaochao/fuel-main,stackforge/fuel-main,ddepaoli3/fuel-main-dev,dancn/fuel-main-dev,stackforge/fuel-main,huntxu/fuel-main,AnselZhangGit/fuel-main,Fiware/ops.Fuel-main-dev