NVP LBaaS: check for association before deleting health monitor

    Bug #1243129 suggests to check for associations before deleting
health monitor in DB logic, so NVP advanced LBaaS should also Change
its operations when deleting a healthmonitor.

Change-Id: I57677cc4b65a13df9f72ec689f34771c7af6a57e
Closes-Bug: #1254639
Check vxlan enablement via modinfo

On some linux distribution, for RHEL 6.5 as an example, vxlan is
enabled but the kernel version is still 2.6. And some linux kernel
version is higher than 3.8 or even 3.11, its vxlan mod may be
disabled. Under both situation, vxlan enablement checking via linux
kernel version may not be correct.

In this patch, we check vxlan enablement via modinfo: if vxlan module
exists and functional test pass, vxlan is enabled.

Closes-Bug: #1267682

Change-Id: Id52c04b4739d2d11fe52d4b1631cb4f39e6b577f
Merge "NVP LBaaS: check for association before deleting health monitor"
Merge "Check vxlan enablement via modinfo"