ceph: update helm version
ceph: update helm version

Currently, Helm v2.5.1 is used, but this version is released in 2017
and a little outdated.
To use the latest version of helm v2.x.x would be beneficial
as we can use more useful Helm commands like `helm template`.

This commit updates Helm version and stop using `helm lint`
with `--strict` option because Helm v2.16.7 does not allow
to use undefined values in values.yaml and
the Helm upstream is now stopping using the `--strict` option.

Signed-off-by: binoue <0e96f1ad4a0682e659ee8de9d3b3e8af33cbd207@cybozu.co.jp>

rook/nfs,rook/nfs,rook/rook,rook/rook,rook/nfs,rook/rook,rook/rook,rook/rook