Add NIC offload disable feature

On some ubuntu kernels with some versions
of Openvswitch and Nicira, when NIC offloading
is enabled on the adapter, the kernel may OOPS
within the openvswitch module.  There is now a flag
to attempt to disable all offload settings for the
adapter prior to openvswitch service startup.

Change-Id: I61b195c69fbb827876de1c3537cece01f36c6db0