NFSv4: Fix a regression in the NFSv4 state manager

Commit 5601a00d (nfs: run state manager
in privileged mode) introduces a regression in the NFSv4 code when
compiled with CONFIG_NFS_V4_1. The calls to nfs4_end_drain_session()
from the main loop in nfs4_state_manager() Oops due to the lack of an
NFSv4.1 session when running NFSv4.0.

The fix is to move those two calls back into nfs41_init_clientid() and
nfs4_reset_session().

The calls to nfs4_end_drain_session() that remain inside
nfs4_state_manager() are safe, since the NFSv4.0 code will never set the
NFS4CLNT_SESSION_DRAINING bit.

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