Avoid race with udev during ovs agent startup

After taking down the veth link between the physical bridge and the integration
bridge call udevadm settle to wait for any udev events to be completely
processed by the operating system before recreating the veth pair.

Some distributions (e.g. openSUSE) have udev rules installed by default that
call e.g. ifdown <interface> during the remove event. If that is processed
after the ovs agent already brought up the veth pair again the veth pair's
link will be down after the agent completed startup and networking will be
broken for all VM instances.

Change-Id: I95520ea96a9804c5261a0c994bbca137535cc37c
Closes-Bug: #1218556
Switch agent report_interval option to float

Being able to set report_interval > 0 and < 1 makes
it easier to consistently reproduce rpc race
conditions.

Change-Id: I4d907159147177e98b043e7e800aea5cf8c23103
Related-Bug: #1224001
Merge "Switch agent report_interval option to float"
Merge "Avoid race with udev during ovs agent startup"