I leave that to you but I I would not bother
After all, this is only a debugging feature, not intended for normal use. In fact, debug-logging in jclouds is disabled by default and it is explicitely enabled by the jclouds plugin, because I think it it is still useful.
If you really insist, I would rather write a logging filter which matches that specific log message and then replaces the binary data by some human-readable placeholder.
If you are experimenting with cloud-init and something does not work as you expected, then there are better ways to debug this and you can always have a look into the decompressed data on your openstack instance directly (it usually can be found somewhere in /var/lib/cloud*/ e.g. on debian it is in /var/lib/cloud/instance/user-data.txt.i)