curl allows SSH connection even if host is not in known_hosts

Summary: Curl does _not_ fail if the SSH host identity cannot be verified due to the host not being included in the `.ssh/known_hosts` file. This makes using curl to login into an previously unknown ssh host system vulnerable to meddler in the middle attacks. When using key based authentication it …

              For SFTP and SCP, this option makes curl skip the known_hosts
              verification.  known_hosts is a file normally stored in the
              user's home directory in the ".ssh" subdirectory, which contains
              hostnames and their public keys.