virsh: Put a new line char after <alias/> in attach-disk

Each attribute is on its own line. We forgot to add new line
character for <alias/>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

tools/virsh-domain.c

@@ -683,7 +683,7 @@ cmdAttachDisk(vshControl *ctl, const vshCmd *cmd)
         virBufferAsprintf(&buf, "<serial>%s</serial>\n", serial);
 
     if (alias)
-        virBufferAsprintf(&buf, "<alias name='%s'/>", alias);
+        virBufferAsprintf(&buf, "<alias name='%s'/>\n", alias);
 
     if (wwn)
         virBufferAsprintf(&buf, "<wwn>%s</wwn>\n", wwn);