Comment 6 for bug 1849502

Reviewed: https://review.opendev.org/691858
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=ce3f2f7d2690eec0dcab4073cbf357b683c6394b
Submitter: Zuul
Branch: stable/train

commit ce3f2f7d2690eec0dcab4073cbf357b683c6394b
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Wed Oct 23 14:47:54 2019 +0000

    Check dnsmasq process is active when spawned

    After spawning the "dnsmasq" process in the method
    "Dnsmasq._spawn_or_reload_process", we need to check that the "dnsmasq"
    process is running and could be detected by the ProcessManager instance
    controlling it.

    ProcessManager determines if a process is "active":
    - If the network ID is in the cmdline used to execute the process.
    - If the process is detected by psutil.Process(pid), returning the
      cmdline needed in the first condition.
    - If the PID file exists; this is written by the dnsmasq process
      once is started and is needed in the second condition.

    To make this feature available for any other process using
    ProcessManager, the implementation is done in this class.

    Change-Id: I51dc9d342c613afcbcfdc50a1d2811502748f170
    Closes-Bug: #1849502
    (cherry picked from commit 7c5ce50a0c9e09d2729ae1ce79d2623ccafca9ee)