kubernetes: Use ijc25/alpine-ssh for ssh_into_kubelet.sh
Much smaller than the CentOS based one.
Note that ijc25/alpine-ssh has entrypoint==ssh.
Drop Compression=yes, this is used for local ssh so no point compressing (just uses CPU).
#!/bin/bash -eux
ssh="docker run --rm -ti \
-v $HOME/.ssh/:/root/.ssh \
- jdeathe/centos-ssh \
+ ijc25/alpine-ssh \
-o LogLevel=FATAL \
-o StrictHostKeyChecking=no \
-o UserKnownHostsFile=/dev/null \
