Do not barf if the VG size is too small; just print a warning

and let it throw an error later if all space is consumed. After
all, each VM can use an arbitrary amount of disk, and eventually
we will have to track it with assign.

clientside/tmcc/linux/xen/libvnode_xen.pm

@@ -399,10 +399,8 @@ sub rootPreConfig()
 
 	my $size = lvmVGSize($VGNAME);
 	if ($size < $XEN_MIN_VGSIZE) {
-	    print STDERR "ERROR: physical disks not big enough to support".
-		" VMs ($size < $XEN_MIN_VGSIZE)\n";
-	    TBScriptUnlock();
-	    return -1;
+	    print STDERR "WARNING: physical disks not big enough to support".
+		" $MAX_VNODES VMs ($size < $XEN_MIN_VGSIZE)\n";
 	}
     }