Better explain incorrect keyfile permissions

[charlieegan3]

Is this a BUG REPORT or FEATURE REQUEST?:

/kind feature

What happened: When running tarmak apply, if the ssh keys have the incorrect permissions, then the apply command fails when connecting to the bastion and spends a long time without a useful error message.

DEBU[0017] check SSH connection to bastion cmd=[ssh -F dev-hub/ssh_config -N bastion /bin/true]  app=tarmak destination=vault-3.tarmak.local                                                  
DEBU[0017] check SSH connection to bastion cmd=[ssh -F dev-hub/ssh_config -N bastion /bin/true]  app=tarmak destination=vault-1.tarmak.local                                                  
DEBU[0017] check SSH connection to bastion cmd=[ssh -F dev-hub/ssh_config -N bastion /bin/true]  app=tarmak destination=vault-2.tarmak.local                                                  
WARN[0017] error checking SSH connecting to bastion: exit status 255  app=tarmak cluster=hub environment=dev stack=vault                                                                      
WARN[0017] error checking SSH connecting to bastion: exit status 255  app=tarmak cluster=hub environment=dev stack=vault                                                                      
WARN[0017] error checking SSH connecting to bastion: exit status 255  app=tarmak cluster=hub environment=dev stack=vault   

What you expected to happen: This is caused by the permissions being incorrect on the ssh key files. I'd expect tarmak to explain this in an error.

How to reproduce it (as minimally and precisely as possible): Set the permissions on the id_rsa files to something wide open and run cluster apply.

Anything else we need to know?: This is worth fixing as it's an issue with our tarmak-config using git-crypt repo pattern.

[charlieegan3]

/kind feature

[JoshVanL]

/assign