CA-151464: Don't assume interface is bonded if master sysfs key exists
CA-151464: Don't assume interface is bonded if master sysfs key exists

In 3.12+ kernels, this key also exists for OVS ports.

Signed-off-by: Si Beaumont <a0992b7f1f450b4c7716d34b81a2d6f0877ae11a@citrix.com>

koushikcgit/xcp-networkd,sharady/xcp-networkd,sharady/xcp-networkd,djs55/xcp-networkd,djs55/xcp-networkd,koushikcgit/xcp-networkd