fix(tests): use single-line lua to avoid multi-document YAML output

tarantoolctl/tt processes a multi-line script line by line and emits a
separate YAML document (---\n...\n) for each line. SnakeYAML's
yaml.load() rejects multi-document streams with
"expected a single document in the stream", which broke 3.x tests
that piped the wait-for-stable script via echo.

Put the script on a single line with ';' separators so the output is
a single YAML document.

Author: dkasimovskiy

tarantool-pooling/src/test/java/io/tarantool/pool/integration/BasePoolTest.java

@@ -98,16 +98,14 @@ protected int getActiveConnectionsCount(TarantoolContainer<?> tt) {
       // 100-500 ms. Wait for it to stabilise (fiber.sleep yields the worker so it
       // can accept the pending connections) before reading the value.
       String lua =
-          "local last = box.stat.net().CONNECTIONS.current\n"
-              + "for i = 1, 50 do\n"
-              + "  require('fiber').sleep(0.05)\n"
-              + "  local cur = box.stat.net().CONNECTIONS.current\n"
-              + "  if cur == last then\n"
-              + "    return cur - 1\n"
-              + "  end\n"
-              + "  last = cur\n"
-              + "end\n"
-              + "return last - 1";
+          "local last = box.stat.net().CONNECTIONS.current;"
+              + " for i = 1, 50 do"
+              + " require('fiber').sleep(0.05);"
+              + " local cur = box.stat.net().CONNECTIONS.current;"
+              + " if cur == last then return cur - 1 end;"
+              + " last = cur;"
+              + " end;"
+              + " return last - 1";
       List<? extends Object> result = TarantoolContainerClientHelper.executeCommandDecoded(tt, lua);
       return (Integer) result.get(0);
     } catch (Exception e) {