[XFS] Retry linux inode cacech lookup if we found a stale inode. This

fixes crashes under high nfs load

SGI-PV: 941429
SGI-Modid: xfs-linux:xfs-kern:197929a

Signed-off-by: Christoph Hellwig <hch@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>