hw/9pfs: Reset server state during TVERSION

hw/9pfs: Reset server state during TVERSION

As per the 9p rfc, during TVERSION its necessary to clean all the active
fids, so that we start the session from a clean state. Its also needed in
scenarios where the guest is booting off 9p, and boot fails, and client
restarts, without any knowledge of the past, it will issue a TVERSION again
so this ensures that we always start from a clean state.

Signed-off-by: Deepak C Shetty <deepakcs@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>