The message with "reject_unknown_hosts" and "abort_on_prompts" is rather
missleading as paramiko returns:
SSHException: Server 'localhost' not found in known_hosts
but fabric reports:
Needed to prompt for a connection or sudo password (host:
localhost), but abort-on-prompts was set to True
This patch handles the special case similarly to existing workarounds.
Signed-off-by: Lukáš Doktor <email@example.com>