Remove kubectl install from prepare-rke

This is needed because prepare-kubectl role can do just the same.
Also fixed rke tests to match.

Change-Id: I808df650a5f755e09c26d13db62ecfc1504a317c
Issue-ID: OOM-1907
Signed-off-by: Michal Zegan <m.zegan@samsung.com>
2 files changed