CP-6167: Fix a bug reported by pylint
CP-6167: Fix a bug reported by pylint

The function _fast_find_tapdisks references errno.ENOENT, but the
errno module is not in scope.

We add a local import (instead of a global one), to follow the same
convention we saw on many other instances in this module.

Signed-off-by: Zheng Li <fff69bf00b8ec5b6098a1768eaaaa75f40b8795d@eu.citrix.com>

siddharthv/sm,BobBall/sm,chandrikas/sm,BobBall/sm,germanop/sm,geosharath/sm,geosharath/sm,martinjorge/sm,malcolmcrossley/sm,martinjorge/sm,chandrikas/sm,pritha-srivastava/sm,geosharath/sm,djs55/sm,robertbreker/sm,djs55/sm,djs55/sm,kostaslamda/sm,robertbreker/sm,malcolmcrossley/sm,chandrikas/sm,robertbreker/sm,kostaslamda/sm,kostaslamda/sm,xapi-project/sm,germanop/sm,xapi-project/sm,martinjorge/sm,pritha-srivastava/sm,BobBall/sm,xapi-project/sm,malcolmcrossley/sm,siddharthv/sm,siddharthv/sm,pritha-srivastava/sm,germanop/sm