In the official document(1), The list of pre-requirement for ssh container has a specification for JVM "Java 1.7 installed".
Our supported configuration site(2) noted that we do support fuse with JVM 1.7 or 1.8, so please add 1.8 on the pre-requirement list.

(1)
https://access.redhat.com/documentation/en-US/Red_Hat_JBoss_Fuse/6.2.1/html/Fabric_Guide/ContSSH.html

(2)
https://access.redhat.com/articles/310603