remove extra mkdir $self->{rootfs} in initialize

The mkdir in intialize is not too helpful since, ve_init, which usually gets
called soon after (`aab init` is followed by `aab bootstrap` in the Makefile)
has a `rmtree $self->{rootfs}` and recreates it directly afterwards again.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>

PVE/AAB.pm

@@ -260,8 +260,6 @@ EOF
 	print $fh "[multilib]\n$servers\n";
     }
 
-    mkdir $self->{rootfs} || die "unable to create rootfs - $!";
-
     $self->logmsg("configured VE $self->{veid}\n");
 }