tag memory leak check on kill server as "leaks"

tests/support/server.tcl

@@ -33,12 +33,14 @@ proc kill_server config {
     if {![dict exists $config "skipleaks"]} {
         catch {
             if {[string match {*Darwin*} [exec uname -a]]} {
+                tags {"leaks"} {
                     test "Check for memory leaks (pid $pid)" {
                         exec leaks $pid
                     } {*0 leaks*}
                 }
             }
         }
+    }
 
     # kill server and wait for the process to be totally exited
     while {[is_alive $config]} {