A new variable "haproxy_stick_table" is added which allows a custom
stick-table to be supplied that is used as the default stick-table
for all haproxy back-ends.
In addition, the variable service.haproxy_stick_table can be defined
for each service to allow a unique stick-table to be supplied for
a particular service.
The old default stick-table definition is removed as there was no
use case defined for it in this role before. An example is added
to defaults/main.yml to show how the custom stick-table can be used
to rate-limit requests that generate 4xx responses which commonly
occur during vulnerability scanning or credential stuffing attacks.
There are many other uses for stick-tables, consult the HAProxy
documentation for details.
Change-Id: I50daba08c10f071157d6450ea2fa97df448f99ec
06e76706c7