IPaddr2: support IPoIB gratuitous arps

This patch allows the configuration of a heartbeat based NFS export of
CXFS clients on a cluster using NFS/IPoIB.

It sends gratuitous arps usin IPoIB by using ipoibarping instead of
send_arp, which relies on libnet and doesn't know IB.

Signed-off-by: Ivan Rayner <ivanr@sgi.com>
Signed-off-by: Anibal Monsalve Salazar <anibal@sgi.com>

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extra : convert_revision : 6ec2b3fe81431eba46c776e46c2ba642515ff0a6