In reference to official JBF docs:
"fabric:container-default-jvm-options, container-default-jvm-options — get or set the default JVM options to use when creating a new container"
link: https://access.redhat.com/documentation/en-US/Red_Hat_JBoss_Fuse/6.1/html/Console_Reference/files/ConsoleFabricContainerDefaultJVMOptions.html

Unfortunately this is only supported by fabric:container-create-ssh in karaf shell. It doesn't work for fabric:container-create-child and when using hawtio at all (even when creating ssh container in hawtio).
So this is a bug because this functionality is missing in above scenarios.

Why it is a blocker?
Consider this scenario:
When you are creating new, secured environment and you are using self signed key for servlets (so then truststore is required), then there is no way to provision containers with hawtio at all (no metter is it SSH or Child) and with fabric:container-create-child. This is because child containers will no be able to do git pull as there is no trustore set (which suppose to be set basing on "zk:set /fabric/configs/io.fabric8.containers.jvmOptions" values).

As there is a bug in "container-default-jvm-options", I have used a workaround: invoked zk:set /fabric/configs/io.fabric8.containers.jvmOptions "your options here" instead of container-default-jvm-options.

This issue is related to:
1. https://issues.jboss.org/browse/FABRIC-351
2. https://github.com/fabric8io/fabric8/issues/2168