res_http_media_cache.c: Set reasonable number of redirects

By default libcurl does not follow redirects, so we explicitly enable
it by setting CURLOPT_FOLLOWLOCATION. Once that is enabled, libcurl
will follow up to CURLOPT_MAXREDIRS redirects, which by default is
configured to be unlimited.

This patch sets CURLOPT_MAXREDIRS to a more reasonable default (8). If
we determine at some point that this needs to be increased on
configurable it is a trivial change.

ASTERISK-29173 #close

Change-Id: I4925ebbcf0c7d728bb9252b3795b3479ae225b30