Update more docker-library images

- `cassandra`: 2.2.12, 2.1.20
- `irssi`: 1.1.1
- `rocket.chat`: 0.61.1

library/cassandra

@@ -4,14 +4,14 @@ Maintainers: Tianon Gravi <admwiggin@gmail.com> (@tianon),
              Joseph Ferguson <yosifkit@gmail.com> (@yosifkit)
 GitRepo: https://github.com/docker-library/cassandra.git
 
-Tags: 2.1.19, 2.1
+Tags: 2.1.20, 2.1
 Architectures: amd64, i386
-GitCommit: ccc145c1950563dc28e05e2f889b084ba95d8387
+GitCommit: f2662126a725065bc524c907a7dcfdbb6e38b31d
 Directory: 2.1
 
-Tags: 2.2.11, 2.2, 2
+Tags: 2.2.12, 2.2, 2
 Architectures: amd64, i386
-GitCommit: ccc145c1950563dc28e05e2f889b084ba95d8387
+GitCommit: 0a8b0c981c2db51bcf15bda01de805f636744073
 Directory: 2.2
 
 Tags: 3.0.15, 3.0

library/irssi

@@ -4,12 +4,12 @@ Maintainers: Jessie Frazelle <acidburn@google.com> (@jessfraz),
              Tianon Gravi <admwiggin@gmail.com> (@tianon)
 GitRepo: https://github.com/jessfraz/irssi.git
 
-Tags: 1.1.0, 1.1, 1, latest
+Tags: 1.1.1, 1.1, 1, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: c03bebcef55d683530f420ba4f13ae87e878e645
+GitCommit: a01102b70c724f1e3415dde1f5181c29675ecd56
 Directory: debian
 
-Tags: 1.1.0-alpine, 1.1-alpine, 1-alpine, alpine
+Tags: 1.1.1-alpine, 1.1-alpine, 1-alpine, alpine
 Architectures: amd64, arm32v6, arm64v8, i386, ppc64le, s390x
-GitCommit: c03bebcef55d683530f420ba4f13ae87e878e645
+GitCommit: a01102b70c724f1e3415dde1f5181c29675ecd56
 Directory: alpine

library/rocket.chat

@@ -1,5 +1,5 @@
 Maintainers: Rocket.Chat Image Team <buildmaster@rocket.chat> (@RocketChat)
 GitRepo: https://github.com/RocketChat/Docker.Official.Image.git
 
-Tags: 0.61.0, 0.61, 0, latest
-GitCommit: 80d0c06e8003d99d5fa9e10e176691a2cdb79987
+Tags: 0.61.1, 0.61, 0, latest
+GitCommit: 2d88f3691d777decb3a8537446d38cd8ae6b62a5