tests: Fix SO_REUSEADDR for TCP tests

Previous allow_reuse_addr was incorrect, it should be
allow_reuse_address. Confirmed looking at setsockopt in strace when
running tcpflushout test.

This is a partial fix for github #386

Author: mkj

test/test_dropbear.py

@@ -76,7 +76,7 @@ def own_venv_command():
 class HandleTcp(socketserver.ThreadingMixIn, socketserver.TCPServer):
 
 	# override TCPServer's default, avoids TIME_WAIT
-	allow_reuse_addr = True
+	allow_reuse_address = True
 
 	""" Listens for a single incoming request, sends a response if given,
 	and returns the inbound data.