mllib, v2v: Allow open_guestfs to set the handle identifier.

Extend open_guestfs to take an optional ?identifier parameter.

Use this parameter in virt-v2v which is currently the only place where
we use the handle identifier.

mllib/common_utils.ml

@@ -363,10 +363,11 @@ let info fs =
 (* Common function to create a new Guestfs handle, with common options
  * (e.g. debug, tracing) already set.
  *)
-let open_guestfs () =
+let open_guestfs ?identifier () =
   let g = new Guestfs.guestfs () in
   if trace () then g#set_trace true;
   if verbose () then g#set_verbose true;
+  may g#set_identifier identifier;
   g
 
 (* All the OCaml virt-* programs use this wrapper to catch exceptions

mllib/common_utils.mli

@@ -152,7 +152,7 @@ val warning : ('a, unit, string, unit) format4 -> 'a
 val info : ('a, unit, string, unit) format4 -> 'a
 (** Standard info function.  Note: Use full sentences for this. *)
 
-val open_guestfs : unit -> Guestfs.guestfs
+val open_guestfs : ?identifier:string -> unit -> Guestfs.guestfs
 (** Common function to create a new Guestfs handle, with common options
     (e.g. debug, tracing) already set. *)
 

v2v/output_rhev.ml

@@ -262,8 +262,7 @@ object
     ?clustersize path format size =
     Changeuid.func changeuid_t (
       fun () ->
-        let g = open_guestfs () in
-        g#set_identifier "rhev_disk_create";
+        let g = open_guestfs ~identifier:"rhev_disk_create" () in
         (* For qcow2, override v2v-supplied compat option, because RHEL 6
          * nodes cannot handle qcow2 v3 (RHBZ#1145582).
          *)

v2v/output_vdsm.ml

@@ -156,8 +156,7 @@ object
 
   method disk_create ?backingfile ?backingformat ?preallocation ?compat
     ?clustersize path format size =
-    let g = open_guestfs () in
-    g#set_identifier "vdsm_disk_create";
+    let g = open_guestfs ~identifier:"vdsm_disk_create" () in
     (* For qcow2, override v2v-supplied compat option, because RHEL 6
      * nodes cannot handle qcow2 v3 (RHBZ#1145582).
      *)

v2v/v2v.ml

@@ -74,8 +74,7 @@ let rec main () =
    | In_place -> message (f_"Opening the source VM")
   );
 
-  let g = open_guestfs () in
-  g#set_identifier "v2v";
+  let g = open_guestfs ~identifier:"v2v" () in
   g#set_network true;
   (match conversion_mode with
    | Copying (overlays, _) -> populate_overlays g overlays

v2v/windows.ml

@@ -72,8 +72,7 @@ let rec copy_virtio_drivers g inspect virtio_win driverdir =
   )
   else if is_regular_file virtio_win then (
     try
-      let g2 = open_guestfs () in
-      g2#set_identifier "virtio_win";
+      let g2 = open_guestfs ~identifier:"virtio_win" () in
       g2#add_drive_opts virtio_win ~readonly:true;
       g2#launch ();
       let vio_root = "/" in