Travis CI: Update config from rabbitmq-common

Travis CI: Update config from rabbitmq-common

Add config schema entry for total_memory_available_override_value

Closes rabbitmq#1445.

[#153501620]

(cherry picked from commit 314f68b)

Update rabbitmq-components.mk

Update rabbitmq-components.mk

Merge branch 'rabbitmq-server-1434' into v3.7.x

Merge pull request rabbitmq#1374 from rabbitmq/rabbitmq-server-995

An option to discard messages if queue is full.

Remove inline comments from example systemd service file

References rabbitmq#1422.

Merge pull request rabbitmq#1413 from rabbitmq/mk-dont-throw-when-con…

…nection-pid-is-non-local

Make rabbit_networking:close_connection/2 more benign

Merge pull request rabbitmq#1413 from rabbitmq/mk-dont-throw-when-con…

…nection-pid-is-non-local

Make rabbit_networking:close_connection/2 more benign