proc.py: Fix RuntimeWarning

ref: benoitc/gunicorn#2146

/usr/lib/python3.9/subprocess.py:941: RuntimeWarning: line buffering (buffering=1) isn't supported in binary mode, the default buffer size will be used
self.stdout = io.open(c2pread, 'rb', bufsize)

mqtt2cmd/proc.py

@@ -50,7 +50,7 @@ def _run_impl(self, cmd, shell):
 
         handle = subprocess.Popen(cmd,
                                   shell=shell,
-                                  bufsize=1,
+                                  # bufsize=1,
                                   stdout=subprocess.PIPE,
                                   stderr=subprocess.STDOUT,
                                   # needed to detach from calling terminal (other wacky things