Add support for setting `SERVER_JVMFLAGS`.

The `SERVER_JVMFLAGS` allows adding some jvm args
to the command line.  This could be used to, for instance,
add remote jmx support.

+ Update the `/usr/bin/zookeeper-server` that comes with the cloudera
package
+ Modify the template to match the packacked version
+ Add writing the template to the recipe if `cloudera`
+ Add a default blank parameter