CA-403700 use iso9660 file system for updates (#6216)

Be explicit about the file system of an update ISO. Remove dead code.

Author: robhoes

ocaml/xapi/xapi_pool_update.ml

@@ -291,7 +291,7 @@ let attach_helper ~__context ~uuid ~vdi ~use_localhost_proxy =
             "/dev/" ^ Client.VBD.get_device ~rpc ~session_id ~self:vbd
         )
       in
-      with_api_errors (mount device) mount_point ;
+      with_api_errors (mount ~ty:(Some "iso9660") device) mount_point ;
       debug "pool_update.attach_helper Mounted %s" mount_point
   ) ;
   let ip =

ocaml/xenopsd/xc/xenops_server_xen.ml

@@ -2465,9 +2465,8 @@ module VM = struct
         | true ->
             Unixext.with_file path [Unix.O_RDONLY] 0o600 f_synced
         | false ->
-            with_mounted_dir_ro path @@ fun dir ->
-            let filename = Filename.concat dir "suspend-image" in
-            Unixext.with_file filename [Unix.O_RDONLY] 0o600 f_synced
+            error "%s: can't mount %s" __FUNCTION__ path ;
+            internal_error "can't mount %s (not a file or block dev)" path
       )
 
   let wait_ballooning task vm =