NFS: Fix up fsync() when the server rebooted

Don't clear the NFS_CONTEXT_RESEND_WRITES flag until after calling
nfs_commit_inode(). Otherwise, if nfs_commit_inode() returns an
error, we end up with dirty pages in the page cache, but no tag
to tell us that those pages need resending.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>