[FIX] longpolling worker: enforce memory limits
[FIX] longpolling worker: enforce memory limits

The GeventServer process was not enforcing the
configured memory limits. In the unlikely event
of a service handling hundreds of concurrent
longpolling requests on hundreds of different
databases, this could render the Registry LRU
ineffective in keeping a low memory footprint.

Even after being evicted from the LRU, these
hundreds of registries would still be referenced
by their in-progress requests, so the memory
would not be freed. An Odoo 10 registry can
typically take 15MB of memory, so this could
become a problem.

ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo