[chore] restore use k8s_cp module to read backup files

[JoelKle]

SUMMARY

Use the k8s_cp Ansible module to read the backup files if we restore AWX.
This simplifies the role.

As proposed from @rooftopcellist in #1111

ISSUE TYPE

• New or Enhanced Feature

ADDITIONAL INFORMATION

My restore test was successful.

[TheRealHaoLiu]

I like it, @jjwatt will do some manual test and maybe add some test automation for backup and restore

are you on our matrix chatroom? come join us! https://matrix.to/#/#awx:ansible.com

[JoelKle]

Thanks for the invitation. You can reach me @JoelKle:matrix.org
I hope i can keep up with the news :)

[rooftopcellist]

@JoelKle Thanks for the contribution!

@jjwatt Here are some notes on how you can go about testing this out. Please reach out if you have any questions!

• https://gist.github.com/rooftopcellist/dbb1183a22d52b24ce35147312664d8f

[rooftopcellist]

I found a bug in the restore role while testing this:

• Unnecessary secrets are created by the Restore role in some cases #1293

But this is unrelated to this PR.

[rooftopcellist]

@JoelKle Thank you for following up on this!