[archiso] Do not use PXE NBD as default.

* Now we have more than one PXE boot methods.
* archiso_ndb_srv= accepts special ${pxeserver} parameter like in others PXE hooks.
* This allows to setup network from initramfs without forcing using a special PXE hook.
* Update README

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

README

@@ -3,7 +3,10 @@ INDEX
 
 * Boot parameters (initramfs stage)
   * hooks/archiso
+  * hooks/archiso_pxe_common
   * hooks/archiso_pxe_nbd
+  * hooks/archiso_pxe_curl
+  * hooks/archiso_pxe_nfs
   * hooks/archiso_loop_mnt
 * Boot parameters (only for configs/releng)
   * etc/rc.conf
@@ -80,7 +83,8 @@ INDEX
 * archiso_nbd_name= Set NBD export name used by the server.
                     Default: archiso
 * archiso_nbd_srv=  Set an IP address where NBD reside.
-                    Default: "${pxeserver}" (The <boot-server-ip from ip=)
+                    If ${pxeserver} is used, PXE IP will be used.
+                    Default: (unset)
 
 
 ** hooks/archiso_pxe_curl

archiso/hooks/archiso_pxe_curl

@@ -2,8 +2,10 @@
 
 run_hook() {
     if [[ -n "${ip}" && -n "${archiso_curl_url}" ]]; then
+
         archiso_curl_url=$(eval echo ${archiso_curl_url})
         [[ -z "${curlspace_size}" ]] && curlspace_size="75%"
+
         mount_handler="archiso_pxe_curl_mount_handler"
     fi
 }

archiso/hooks/archiso_pxe_nbd

@@ -1,9 +1,10 @@
 # vim: set ft=sh:
 
 run_hook() {
-    if [[ -n "${ip}" ]]; then
+    if [[ -n "${ip}" && -n "${archiso_nbd_srv}" ]]; then
+
+        archiso_nbd_srv=$(eval echo ${archiso_nbd_srv})
         [[ -z "${archiso_nbd_name}" ]] && archiso_nbd_name="archiso"
-        [[ -z "${archiso_nbd_srv}" ]] && archiso_nbd_srv="${pxeserver}"
 
         mount_handler="archiso_pxe_nbd_mount_handler"
     fi