bugfix: netInfo can be null even when there is connectivity.

[gmale]

This bug resulted in MixPanel requests never being sent in our locked-down Ethernet Kiosk environment, as referenced in Issue #444

From our investigation, it is worth noting that:

• We have connectivity via Ethernet
• We have the android.permission.ACCESS_NETWORK_STATE permission enabled
• connectivityManager.getActiveNetworkInfo() always returns null
• connectivityManager.getAllNetworks() always returns either null or an empty array (on API 22)

Also, according to the documentation for ConnectivityManager#getActiveNetworkInfo:

This may return null when there is no default network.

The code in HttpService was assuming that a null NetworkInfo response signifies no connectivity but that is not always the case. In our Ethernet environment, we have connectivity but there is no default network.

[patedit]

@gmale This is great. Thanks for the investigation and for implementing a fix. Will merge now and release it later today.