fix(client): adjust indentation in keys_add function

While running deis keys:add , if there are no keys the client is printing No SSH public keys found and throwing an error .
Adjusted the indendation , So if client dont find the public keys prints No SSH public keys and prints usage deis keys:add [<key>]
Merge pull request #1077 from smothiki/smothiki-keys-add-fix

fix(client): adjust indentation in keys_add function