rabbit: Stop rabbitmq_prelaunch if we fail to start rabbit

[Why]
This is important if the environment changes between that error and the
next attempt to start `rabbit': the environment is only read during the
start of `rabbitmq_prelaunch' (and the cached context is cleaned on
stop).

This fixes a transient failure of the
`unit_log_management_SUITE:log_file_fails_to_initialise_during_startup/1`
testcase.

V2: Explicitly ignore the return value of `application:stop/1`.
(cherry picked from commit 87a8c15)

Author: dumbbell

deps/rabbit/src/rabbit.erl

@@ -428,6 +428,16 @@ start_it(StartType) ->
                 ok
             catch
                 error:{badmatch, Error}:_ ->
+                    %% `rabbitmq_prelaunch' was started before `rabbit' above.
+                    %% If the latter fails to start, we must stop the former as
+                    %% well.
+                    %%
+                    %% This is important if the environment changes between
+                    %% that error and the next attempt to start `rabbit': the
+                    %% environment is only read during the start of
+                    %% `rabbitmq_prelaunch' (and the cached context is cleaned
+                    %% on stop).
+                    _ = application:stop(rabbitmq_prelaunch),
                     stop_boot_marker(Marker),
                     case StartType of
                         temporary -> throw(Error);