Whitespace: Reformat Pool.create_VLAN_from_PIF

$ camlp4o -printer o -no_comments xapi_pool.ml | md5sum
6afb19c9cff915091d37775375954312

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
CA-106560: Create VLANs on slaves that are in 'Maintenance Mode'

Weaken the condition for creating VLANs on slaves during
a Pool.create_VLAN_from_PIF from hosts that are enabled to hosts that are live
(according to the host metrics). This enables the VLAN to be created on slaves
that are in XenCenter's 'Maintenance Mode'.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>