Update memcached

Changes:

- https://github.com/docker-library/memcached/commit/8376d3e: Merge pull request https://github.com/docker-library/memcached/pull/54 from moisesguimaraes/master
- https://github.com/docker-library/memcached/commit/206a6c4: Temporarily update OpenSSL config to allow tests to pass
- https://github.com/docker-library/memcached/commit/e6a5d36: Hold alpine TLS for now.
- https://github.com/docker-library/memcached/commit/26f0f04: Add TLS support

library/memcached

@@ -6,7 +6,7 @@ GitRepo: https://github.com/docker-library/memcached.git
 
 Tags: 1.5.20, 1.5, 1, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, i386, ppc64le, s390x
-GitCommit: 3939abc659b8c72e10484d3771b4b15234b840ca
+GitCommit: 206a6c4dcbed0652885e716717653fc87de53bd0
 Directory: debian
 
 Tags: 1.5.20-alpine, 1.5-alpine, 1-alpine, alpine