NuPlayer: Use ".m3u8" in substring search to determine HLS URL

In IsHTTPLiveURL(), "m3u8" is being used in sub-string comparison
to determine if the given URL is HTTPLiveURL or not.

This can lead to false results incase if the given URL has
"m3u8" as part of it.

Hence use ".m3u8" in strstr() instead of "m3u8".

Change-Id: I7f4a3c641d831b3ef77d166701f3e3edabdaebc0