In short, this is related to https://issues.jboss.org/browse/ENTESB-2760, but the workaround / fix "client -l 0" only works for client and not "fabric:container-connect"

---------
In the fuse.log, they found error log
Server at XXX presented unverified DSA key: YYYY

Looking into the issue, when user login to root container and make a request via fabric:container-connect

2017-05-29 08:56:42,015 | INFO | 1]-nio2-thread-2 | ChannelSession | 158 - org.apache.sshd.core - 0.14.0 | Executing command: container-connect <child_container> camel:route-list n |

2017-05-29 08:56:56,015 | INFO | 1]-nio2-thread-1 | ChannelSession | 158 - org.apache.sshd.core - 0.14.0 | Executing command: container-connect <child_container> activemq:dstat n |

So, someone login <root> and run "container-connect" to <child_container> and execute some commands. Under container-connect it uses sshd and didn't have an option to lower the debug level. [1]

[1]
fabric8-fabric8-1.2.0.redhat-630630224-03/fabric/fabric-commands/src/main/java/io/fabric8/commands/ContainerConnectAction.java