CA-135095: don't stop probing devices on error

When tapback needs to exit (e.g. the XenStore node has been removed), it
needs to tear down all devices, and this might fail because some
tapdisks might have already been closed by the SM. This patch ensures
that all devices are torn down.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Acked-by: Germano Percossi <germano.percossi@citrix.com>
CP-8454: log message when disconnecting from the ring

tapdisk logs a message when it implicitly disconnects from the ring at
tap-ctl close time, this helps debugging.

In addition, clarify what "(created)" means in the log.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
CA-135531: fix control socket for slaves

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
Reviewed-by: Vineeth Raveendran <vineeth.thampi@citrix.com>

GitHub: closes #81 on xapi-project/blktap
implement page pool init
implement page pool init
implement page pool init
implement page pool init
implement page pool init
implement page pool init
implement page pool init
implement page pool init
implement page pool init