Increase lease time for dhcp agent
Increase lease time for dhcp agent

Usually failover takes a couple of minutes. 120 seconds is not enough so
during failover VMs loose IP address, breaking the connectivity.
Increasing the value to 600 allows

* Minimaze the number of DHCPDISCOVER requests during failover
* Minimaze the load on dnsmasq as it will be less frequently renewing IP
  addresses for VMs

Change-Id: I7dc57e3f79ed8ee5e83c26e0c80d6a44e0840b4a
Closes-Bug: 1371104

xarses/fuel-library,SmartInfrastructures/fuel-library-dev,SmartInfrastructures/fuel-library-dev,eayunstack/fuel-library,zhaochao/fuel-library,zhaochao/fuel-library,ddepaoli3/fuel-library-dev,zhaochao/fuel-library,xarses/fuel-library,huntxu/fuel-library,SmartInfrastructures/fuel-library-dev,huntxu/fuel-library,ddepaoli3/fuel-library-dev,stackforge/fuel-library,huntxu/fuel-library,ddepaoli3/fuel-library-dev,stackforge/fuel-library,eayunstack/fuel-library,SmartInfrastructures/fuel-library-dev,eayunstack/fuel-library,xarses/fuel-library,ddepaoli3/fuel-library-dev,eayunstack/fuel-library,stackforge/fuel-library,zhaochao/fuel-library,SmartInfrastructures/fuel-library-dev,stackforge/fuel-library,zhaochao/fuel-library,eayunstack/fuel-library,xarses/fuel-library,ddepaoli3/fuel-library-dev,huntxu/fuel-library,huntxu/fuel-library