Forbid new-line char in name of new domain

Forbid new-line char in name of new domain

New line character in name of domain is now forbidden because it
mess virsh output and can be confusing for users.
Validation of name is done in drivers, after parsing XML to avoid
problems with dissappeared domains which was already created with
new-line char in name.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>