IP monitor is a method that is going to be executed in a separate
process, to monitor the IP addresses changes in a namespace.
This method spawns a thread to read from a socket opened by Pyroute2.
The read function is a blocking method that will end only when the
socket is closed. To avoid thread starvation that can happen using
greenthreads, IP monitor will use kernel threads.
This will increase the resources used but will ensure that no message
is lost when reading the monitor socket.
Reduced the number of IPs generated in "test_add_and_remove_multiple_ips"
to shrink the testing time used.
Change-Id: I3fbba2854d40ab0f683443aa30c2a95752345d2e
Closes-Bug: #1849547
48730d9449