Do not error if the platform does not support restricting the MAXSEG
Do not error if the platform does not support restricting the MAXSEG

Some depressing platforms don't support this. The intent is to work
around incorrect MTU settings for a network, which is hopefully rare,
so being opportunistic without being fatalistic seems a wise course.

Change-Id: I2108f335bdf623f6fc0a1723a8b5988c253a76b3

openstack/pyghmi,stackforge/pyghmi,openstack/pyghmi