encrypted ssh keys are overwritten if a pass_phrase is not defined

[cfortier2]

If you attempt to use an existing encrypted ssh_key but do not provide a pass_phrase, the keyformatter can't read key and is 'rescued' by returning nil.

The private_key class receives a 'nil' key and generates then overwrites the existing key.

[cfortier2]

the issue can be replicated by:
create encrypted ssh keys
add those keys to AWS account

run chef-metal with a block like:
fog_key_pair 'foo' do
private_key_path "#{ec2keydir}/foo"
public_key_path "#{ec2keydir}/foo.pub"
end

chef will error out with mismatched fingerprints and the original ssh key will be overwritten.

[lamont-granquist]

this is rather bad.