Merge pull request #6715 from scientificlinux/sl6

Update sl container for sl6 to current (build-date=20191001)

library/sl

@@ -15,4 +15,4 @@ Tags: 6
 Architectures: amd64
 GitFetch: refs/heads/6
 Directory: sl6
-GitCommit: b68ea8646e12bd67065fc0c518bd4ec8716f6afd
+GitCommit: b4bcf2e705249e993cec0bf4785f4cd2371236b2