Default to Charmed Install

OpenEBS is giving us troubles again, so we need to use the --charmed option
in the installer until we can figure out how to fix the K8s installer.

Change-Id: I6dcd24f9b7c1f70d074bcd40f63fb110fb1c355b
Signed-off-by: beierlm <mark.beierl@canonical.com>