NFS: Eliminate nfs_renew_times()

The nfs_renew_times() function plants the current time in jiffies in
dentry->d_time.  But a call to nfs_renew_times() is always followed by
another call that overwrites dentry->d_time.  Get rid of the
nfs_renew_times() calls.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>