Reset failures count once a read succeed

The failure counter was for the entire playback’s duration. So should more than 5 read failures occurred, regardless of time, playback would have been interrupted.
As soon as a read succeed, reset the failure count to 0.

Ref #12113
Revert "Prevent MythSocket::Read from returning an error, when there’s just no data available yet"

This reverts commit 0dfa2b3c4c6bf6a45f760f385d41fcd3975639c9.