Make innodb pool size configurable

Alows configuring of buffer pool size and decreases default
value to 100MB.

For VMs with 2G RAM is 592MB buffer too big. Then you can hit
an issue that openstack requests fail because there is not
enough memory to spawn new process or mysql server restart fails
for because it fails to allocate 592MB buffer.

Change-Id: I9126c090d3d4cd03cb93735a2b0c54fa250eed61
Merge "Make innodb pool size configurable"