[PATCH] kNFSd: correct symlink related error returns.

[PATCH] kNFSd: correct symlink related error returns.

From: NeilBrown <neilb@cse.unsw.edu.au>

unlike v2/v3, nfsv4 returns nfserr_inval when attempting to read, write,
commit or test lock a symlink.  nfsv4 does return nfserr_symlink on lookup
and open, so a simple fix in fh_verify() will not work.