Tune apache connection limits down
Tune apache connection limits down

We are facing memory pressure in gate testing. Apache is fairly large so
tune its connection limits down to try and squeeze out more useable
memory. THis should be fine for dev envs, also tlsproxy is not enabled
by default so we can check that this tuning works well on a subset of
jobs before making it default everywhere.

Data comparisons done with gate-tempest-dsvm-neutron-full-ubuntu-xenial
jobs.

Old: http://logs.openstack.org/37/447037/2/check/gate-tempest-dsvm-neutron-full-ubuntu-xenial/721fc6f/logs/screen-peakmem_tracker.txt.gz
       PID   %MEM             RSS       PPID       TIME     NLWP WCHAN                     COMMAND
     20504    0.2           16660      19589   00:00:00       34 -                         /usr/sbin/apache2 -k start
     20505    0.2           16600      19589   00:00:00       34 -                         /usr/sbin/apache2 -k start
     20672    0.2           16600      19589   00:00:00       34 -                         /usr/sbin/apache2 -k start
     20503    0.1           14388      19589   00:00:00       34 -                         /usr/sbin/apache2 -k start
     19589    0.1            9964          1   00:00:00        1 -                         /usr/sbin/apache2 -k start
Total RSS: 74212

New: http://logs.openstack.org/41/446741/1/check/gate-tempest-dsvm-neutron-full-ubuntu-xenial/fa4d2e6/logs/screen-peakmem_tracker.txt.gz
       PID   %MEM             RSS       PPID       TIME     NLWP WCHAN                     COMMAND
      8036    0.1           15316       8018   00:00:01       34 -                         /usr/sbin/apache2 -k start
      8037    0.1           15228       8018   00:00:01       34 -                         /usr/sbin/apache2 -k start
      8018    0.1            8584          1   00:00:00        1 -                         /usr/sbin/apache2 -k start
Total RSS: 39128

Note RSS here is in KB. Total difference is 35084KB or about
34MB. Not the biggest change, but we seem to be functional and it
almost halves the apache overhead.

Change-Id: If82fa347db140021197a215113df4ce38fb4fd17

richliu/devstack,dtroyer/devstack,nawawi/openstack,openstack-dev/devstack,richliu/devstack,nawawi/openstack,group-policy/devstack,dtroyer/devstack,noironetworks/devstack,noironetworks/devstack,group-policy/devstack,openstack-dev/devstack