oxenstored: Fix process.ml build after 070ab4c505

This change:
  070ab4c505
  "oxenstored: Protect oxenstored from malicious domains"
broke the build because it had an unresolved semantic (but not
textual) conflict with
  c69fddbd5d
  "tools/ocaml: Remove log library from tools/ocaml/libs"
(which is in 4.2 but not 4.1)

Fix this by using the 4.1.x idiom in the new error handling introduced
in 070ab4c505.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: David Scott <dave.scott@eu.citrix.com>

tools/ocaml/xenstored/process.ml

@@ -372,8 +372,8 @@ let do_input store cons doms con =
 		try
 			Connection.do_input con
 		with Failure exp ->
-			error "caught exception %s" exp;
-			error "got a bad client %s" (sprintf "%-8s" (Connection.get_domstr con));
+			Logs.error "general" "caught exception %s" exp;
+			Logs.error "general" "got a bad client %s" (sprintf "%-8s" (Connection.get_domstr con));
 			Connection.mark_as_bad con;
 			false
 	in