In quotaoff(), lock the vnode instead of asserting it when manipulating v_vflags.
In quotaoff(), lock the vnode instead of asserting it when manipulating
v_vflags.

MFC after:	1 week
Submitted by:	Antoine Brodin <antoine at brodin at laposte dot net>

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase