Add additional exception to prevent socket.gaierror error

In time of second host, you need to pass FQDN of first host to
receive answer file, but FQDN not pass any validation and can be
incorrect, it will lead to socket.gaierror in socket.getaddrinfo
method.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1136015

Change-Id: I92776791af606b6fdb664c9e44ed119a167d15ac
Signed-off-by: Artyom Lukianov <alukiano@redhat.com>
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>