Test: do not complain when "leaks" can't run because process died.

tests/support/server.tcl

@@ -40,6 +40,10 @@ proc kill_server config {
                     test "Check for memory leaks (pid $pid)" {
                         set output {0 leaks}
                         catch {exec leaks $pid} output
+                        if {[string match {*process does not exist*} $output]} {
+                            # In a few tests we kill the server process.
+                            set output "0 leaks"
+                        }
                         set output
                     } {*0 leaks*}
                 }