[mythtv-cmyth] Add more logging to OpenLiveStream

- Log on "done"
- Log on fail case
[cmyth] Fix switching to first file on setting up Live TV chain

This fixes a crash that was reported when using analog tuners or pre 0.25 backends.

The current chain element is -1, so switch dir(ection) should be 1 to switch to
the next one. Fixed by calling cmyth_livetv_chain_switch_last().

Trace:
Program terminated with signal 11, Segmentation fault.
0 0x00007fa2441a27ef in cmyth_livetv_chain_seek (whence=<optimized out>,
        offset=0, rec=0x7fa21c0bc188) at livetv.c:1103
  1103 offset += rec->rec_livetv_chain->chain_files[cur]->file_req;

Fixes #99
[cmyth] Return error (-1) on seek out of range

- cmyth_file_seek():
  Return -1 on invalid seek.
- cmyth_livetv_chain_seek():
  WHENCE_SET: Wanted "current" should be less than chain "count" else the seek cannot to be provided. So return error.
[cmyth] Set seek buffer in cmyth_file_seek to 4K