MFC: r316694
Fix a crash during unmount of an NFSv4.1 mount.
Larry Rosenman reported a crash on freebsd-current@ which was caused by
a premature release of the krpc backchannel socket structure.
I believe this was caused by a race between the SVC_RELEASE() in clnt_vc.c
and the xprt_unregister() in the higher layer (clnt_rc.c), which tried
to lock the mutex in the xprt structure and crashed.
This patch fixes this by removing the xprt_unregister() in the clnt_vc
layer and allowing this to always be done by the clnt_rc (higher reconnect
layer).
git-svn-id: svn://svn.freebsd.org/base/stable/10@317473
ccf9f872-aa2e-dd11-9fc8-
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