BREAKING: Remove support for Debian 9 and Ubuntu 16.04

- Deprecate Debian 9 and Ubuntu 16.04
- Add support for Debian 10
- Remove RABBITMQ_USE_LONGNAME in clustering acceptance tests
  Acceptance tests fail on instance without a FQDN when
  `RABBITMQ_USE_LONGNAME` is set to `true` in the environment.
  Simplify the test case; this still seems to work on older and newer
  supported versions

Signed-off-by: William Yardley <wyardley@users.noreply.github.com>

Author: wyardley

metadata.json

@@ -23,13 +23,12 @@
     {
       "operatingsystem": "Debian",
       "operatingsystemrelease": [
-        "9"
+        "10"
       ]
     },
     {
       "operatingsystem": "Ubuntu",
       "operatingsystemrelease": [
-        "16.04",
         "18.04"
       ]
     },

spec/acceptance/clustering_spec.rb

@@ -11,7 +11,6 @@ class { 'rabbitmq':
         config_cluster           => true,
         cluster_nodes            => ['rabbit1', 'rabbit2'],
         cluster_node_type        => 'ram',
-        environment_variables    => { 'RABBITMQ_USE_LONGNAME' => true },
         erlang_cookie            => 'TESTCOOKIE',
         wipe_db_on_cookie_change => false,
       }
@@ -37,7 +36,6 @@ class { 'rabbitmq':
         config_cluster           => true,
         cluster_nodes            => ['rabbit1', 'rabbit2'],
         cluster_node_type        => 'ram',
-        environment_variables    => { 'RABBITMQ_USE_LONGNAME' => true },
         erlang_cookie            => 'TESTCOOKIE',
         wipe_db_on_cookie_change => true,
       }
@@ -83,7 +81,7 @@ class { 'rabbitmq':
         config_cluster           => true,
         cluster_nodes            => ['foobar', 'rabbit2'],
         cluster_node_type        => 'ram',
-        environment_variables    => { 'RABBITMQ_USE_LONGNAME' => true, 'NODENAME' => 'rabbit@foobar' },
+        environment_variables    => { 'NODENAME' => 'rabbit@foobar' },
         erlang_cookie            => 'TESTCOOKIE',
       }
       if $facts['os']['family'] == 'RedHat' {