CLOUDSTACK-7820: Don't consider disabled hosts for calculating disable threshold.
CLOUDSTACK-7821: Fix OSX cannot connect to VPN due to wrongly declaim ENCAPSULATION_MODE_UDP_TRANSPORT_RFC

OSX always declaims it's behind NAT no matter it's true or not, thus result in
confusion of openswan.

Add parameter "forceencaps=yes" to openswan to make sure non NAT VPN connection
from OSX can pass through.