CLOUDSTACK-6712: NPE in findJobInstanceUuid() in ApiDBUtils
CLOUDSTACK-6714: monitor script echo service command is added with quotes
releasing dhcp leases on vpcs failes because the network tier of the tennant aren't behinbd eth0. Here we make interface selection dynamic.

Signed-off-by: Daan Hoogland <daan@onecht.net>
A slightly more reliable way of extracting the device name. Thanks John.

Signed-off-by: Daan Hoogland <daan@onecht.net>