[rabbitmq] Add information on maybe_stuck() processes for RMQ

We have seen environments in which simple commands such as

    rabbitmqctl list_queues

Get stuck and do not produce any output. We found it helpful to run

    rabbitmqctl eval 'rabbitmq_diagnostics:maybe_stuck().'

To obtain a list of "stuck" Erlang processes for further analysis.
This change adds the output of the above command to the sosreport.

Depends-On: #2232
Closes: https://bugs.launchpad.net/ubuntu/+source/sosreport/+bug/1890846
Resolves: #2189

Signed-off-by: Nicolas Bock <nicolas.bock@canonical.com>
Signed-off-by: Jake Hunsaker <jhunsake@redhat.com>

sos/report/plugins/rabbitmq.py

@@ -37,8 +37,16 @@ def setup(self):
                     self.fmt_container_cmd(container, 'rabbitmqctl report'),
                     foreground=True
                 )
+                self.add_cmd_output(
+                    self.fmt_container_cmd(
+                        container, "rabbitmqctl eval "
+                        "'rabbit_diagnostics:maybe_stuck().'"),
+                    foreground=True
+                )
         else:
             self.add_cmd_output("rabbitmqctl report")
+            self.add_cmd_output(
+                "rabbitmqctl eval 'rabbit_diagnostics:maybe_stuck().'")
 
         self.add_copy_spec([
             "/etc/rabbitmq/*",