MFC: r235381

MFC: r235381
Fix two cases in the new NFS server where a tsleep() is
used, when the code should actually protect the tested
variable with a mutex. Since the tsleep()s had a 10sec
timeout, the race would have only delayed the allocation
of a new clientid for a client. The sleeps will also
rarely occur, since having a callback in progress when
a client acquires a new clientid, is unlikely.
in practice, since having a callback in progress when
a fresh clientid is being acquired by a client is unlikely.

git-svn-id: svn://svn.freebsd.org/base/stable/8@236888 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f