Fix stat & TestCLI#test_control_for_tcp

[MSP-Greg]

No description provided.

[MSP-Greg]

@nateberkopec

Thought an explanation might be helpful, as I don't know puma that well. Most of the intermittent failures originally fail with something like the following:

TestCLI#test_control_for_tcp = [MinitestRetry] retry 'test_control_for_tcp' count: 1,  msg: --- expected
+++ actual
@@ -1 +1,2 @@
-"{ \"backlog\": 0, \"running\": 0 }"
+# encoding: ASCII-8BIT
+"{ \"backlog\": , \"running\":  }"

The output shown at the bottom of the log is the retry info. So, from the above, we see two things:

1. The split command is not working in /test/test_cli.rb. Hence, the change from "\r\n" to /\r?\n/ for the delimiter.

2. The last line has no zeros. The backlog and running attributes from lib/puma/server.rb are shown below:

    def backlog
      @thread_pool and @thread_pool.backlog
    end

    def running
      @thread_pool and @thread_pool.spawned
    end

That code shows that @thread_pool may be nil, and hence, the return will either be nil or a number >= 0. Hence, the added || 0 code to lib/puma/cluster.rb and lib/puma/single.rb for their 'stats' info.

This fixes the issue with the test, but I don't know if the test code should generate a non nil value for @thread_pool, and hence there really is an issue... Thanks, Greg