lxc-ubuntu-cloud: Update arm* cross

| host arch | arm64 | armhf | armel |
-------------------------------------
| arm64     |   X   |   X   |   X   |
| armhf     |       |   X   |   X   |
| armel     |       |   X   |   X   |
-------------------------------------

Although optional, all existing arm64 silicon supports 32bit instructions.
armel/armhf is only a userspace change, so they are interchangeable.
However armhf isn't supported on all armel platforms (e.g. armv6) but
all those we support have hard-float.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>

templates/lxc-ubuntu-cloud.in

@@ -235,7 +235,10 @@ fi
 if [ "$skip_arch_check" = "0" ]; then
     case "$hostarch:$arch" in
         $arch:$arch) : ;; # the host == container
-        amd64:i386|arm*:arm*) :;; # supported "cross"
+        amd64:i386) :;; # supported "cross"
+        arm64:arm*) :;; # supported "cross"
+        armel:armhf) :;; # supported "cross"
+        armhf:armel) :;; # supported "cross"
         *) echo "cannot create '$arch' container on hostarch '$hostarch'";
            exit 1;;
     esac