NFSv4: Fix an NFSv4 mount regression

Commit 008f55d0 (nfs41: recover lease in
_nfs4_lookup_root) forces the state manager to always run on mount. This is
a bug in the case of NFSv4.0, which doesn't require us to send a
setclientid until we want to grab file state.

In any case, this is completely the wrong place to be doing state
management. Moving that code into nfs4_init_session...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>