Update rabbitmq

Changes:

- https://github.com/docker-library/rabbitmq/commit/9a93fc4: Update to 3.7.15, Erlang/OTP 22.0.4, OpenSSL 1.1.1c
- https://github.com/docker-library/rabbitmq/commit/54957da: Update to 3.8.0-beta.4, Erlang/OTP 22.0.4, OpenSSL 1.1.1c
- https://github.com/docker-library/rabbitmq/commit/30392da: Update generated README

library/rabbitmq

@@ -6,7 +6,7 @@ GitRepo: https://github.com/docker-library/rabbitmq.git
 
 Tags: 3.8.0-beta.4, 3.8-rc
 Architectures: amd64, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 134272810421b08ad6f467ab6f3197442cf05412
+GitCommit: 54957dadc2ed1799a7ba58e352ca35b8fa214317
 Directory: 3.8-rc/ubuntu
 
 Tags: 3.8.0-beta.4-management, 3.8-rc-management
@@ -16,7 +16,7 @@ Directory: 3.8-rc/ubuntu/management
 
 Tags: 3.8.0-beta.4-alpine, 3.8-rc-alpine
 Architectures: amd64, arm32v6, arm64v8, i386, ppc64le, s390x
-GitCommit: 134272810421b08ad6f467ab6f3197442cf05412
+GitCommit: 54957dadc2ed1799a7ba58e352ca35b8fa214317
 Directory: 3.8-rc/alpine
 
 Tags: 3.8.0-beta.4-management-alpine, 3.8-rc-management-alpine
@@ -26,7 +26,7 @@ Directory: 3.8-rc/alpine/management
 
 Tags: 3.7.15, 3.7, 3, latest
 Architectures: amd64, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: e052620f1213fabac11b11d012ad683a45dcfcb3
+GitCommit: 9a93fc44d5d8f0224c7ab33fb2bf3767d6ad45d3
 Directory: 3.7/ubuntu
 
 Tags: 3.7.15-management, 3.7-management, 3-management, management
@@ -36,7 +36,7 @@ Directory: 3.7/ubuntu/management
 
 Tags: 3.7.15-alpine, 3.7-alpine, 3-alpine, alpine
 Architectures: amd64, arm32v6, arm64v8, i386, ppc64le, s390x
-GitCommit: e052620f1213fabac11b11d012ad683a45dcfcb3
+GitCommit: 9a93fc44d5d8f0224c7ab33fb2bf3767d6ad45d3
 Directory: 3.7/alpine
 
 Tags: 3.7.15-management-alpine, 3.7-management-alpine, 3-management-alpine, management-alpine