Fixes to asset manager to ensure there is no crash on DNS resolver as well as no hanging if connection breaks during download

This patch fixes the AssetsManager by ensuring that proper curl settings are done

AssetsManager (and the app using it) crash if CURLOPT_NOSIGNAL is not set and there is a DNS resolution issue.  This is a non bug in curl on systems using posix threads and the recommended fix is applied here.

The assets manager perpetually waits if there is a connection timeout and does not recover if the connection is resumed. The speed limit checks enable curl to abort the download if there is a network connectivity issue during download.