Remove ssh hard dependency on a user's homedir.

Fixes issue #13458.

If the key lives under a user's homedir then there is still
a requirement of the homedir existing.  This is to preserve the previous
behavior.
Merge branch 'develop' of https://github.com/saltstack/salt into fix_13458
Merge pull request #14335 from hazaelsan/fix_13458

Fix 13458