wait_server_start: warn if lsof is not available

If lsof is not available, wait_server_start uses a fixed timeout,
which can trigger a race condition if the timeout turns out to be too
short. Emit a warning so that we know this is going on from the test
logs.

tests/compat.sh

@@ -887,6 +887,7 @@ if type lsof >/dev/null 2>/dev/null; then
         done
     }
 else
+    echo "Warning: lsof not available, wait_server_start = sleep"
     wait_server_start() {
         sleep 2
     }

tests/ssl-opt.sh

@@ -308,6 +308,7 @@ if type lsof >/dev/null 2>/dev/null; then
         done
     }
 else
+    echo "Warning: lsof not available, wait_server_start = sleep $START_DELAY"
     wait_server_start() {
         sleep "$START_DELAY"
     }