High memory usage by neutron-server

Issue

• Neutron server is consuming almost 100% of the ram memory on controller nodes and affecting other services.
• Controllers must be restarted every few days

• Running top shows this on the controllers:

  top - 10:49:22 up 25 days, 16:35,  1 user,  load average: 1.56, 19.64, 17.42
  Tasks: 1692 total,   8 running, 1684 sleeping,   0 stopped,   0 zombie
  %Cpu(s):  3.7 us,  1.4 sy,  0.0 ni, 94.6 id,  0.0 wa,  0.1 hi,  0.2 si,  0.0 st
  MiB Mem : 128277.0 total,  10385.7 free, 113862.0 used,   4029.3 buff/cache
  MiB Swap:      0.0 total,      0.0 free,      0.0 used.  13266.5 avail Mem
  
      PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
  291421 42435     20   0 8744164   8.1g   5944 S   0.0   6.5  28:54.96 neutron-server:
  291428 42435     20   0 8650128   8.0g   5976 R   1.0   6.4  27:10.57 neutron-server:
  291430 42435     20   0 8589320   8.0g   6056 R   0.0   6.4  26:06.40 neutron-server:
  291419 42435     20   0 8545504   7.9g   5904 S   1.9   6.3  28:04.05 neutron-server:
  291420 42435     20   0 8433128   7.8g   6048 S   0.0   6.2  25:41.63 neutron-server:
  291427 42435     20   0 7129752   6.6g   6052 S   0.0   5.3  23:09.03 neutron-server:
  291425 42435     20   0 6729908   6.2g   6048 R   0.0   5.0  22:43.35 neutron-server:
  291424 42435     20   0 6595756   6.1g   5940 R   1.0   4.8  23:05.74 neutron-server:
  291422 42435     20   0 6587280   6.1g   5984 S   0.0   4.8  23:29.10 neutron-server:
  291429 42435     20   0 5509292   5.0g   6052 R   0.0   4.0  23:10.26 neutron-server:
  11615 42409     20   0 6742660 497088      0 S   0.0   0.4  49:19.12 collectd-sensub
  859464 42435     20   0  605720 380064   6044 S   0.0   0.3   1:00.43 neutron-server: