- add back default config from the 3.5.8 package as 3.6.6 doesn't
ship one anymore
- rabbitmq-script-wrapper now directly talks to the scripts in
_rabbit_erllibdir instead of having another indirection.
- moved tmpfiles.d support into the main systemd install block
- extracted make cmdline options into a variable

- update to 3.6.6
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_6
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_5
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_4
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_3
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_2
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_1
https://github.com/rabbitmq/rabbitmq-server/releases/tag/rabbitmq_v3_6_0