Use "ip link" to find the MAC address and MTU of a NIC

Previously, we used "ip address", but this does not work in newer
versions of iproute2 for NICs that don't have an IP address.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Get xapi to tell xapissl directly what stunnel must listen on

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Ensure (by mutex) that only one "stunnel restart" runs at a time

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Xapi_http: don't retry binding if kernel does not support protocol

In other words: do not waste time retrying binding to an IPv6 address
if the kernel does not support IPv6.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Merge pull request #1157 from robhoes/master

Changes to support newer versions of iproute2 in dom0