Fix net tests on stm32f4dis-nuttx

[rtakacs]

The following net tests are failing (caused by #851):

• test_net_1.js
• test_net_2.js
• test_net_4.js
• test_net_5.js
• test_net_6.js
• issue-266.js

You can check it on the testresult webpage: https://samsung.github.io/iotjs-test-results/