Running processSource twice with same URI restarts download

[nbolender]

If you run processSource twice in quick succession with the same image URI (like when networkAvailability becomes true), the component cancels the in-progress download and starts a new one. Some race conditions exist with RNFS to cause errors or the display of blank images.

I'm not sure what the cause is just yet, but for now I am disabling the network check as a workaround on my production app.