igt_kms extensively uses line continuation when dumping state updates
at the debug level. They got badly mangled with the recent changes to
for the log handling functions. Two separate fixes:
- Don't prepend domain and other metainformation when it's just a
  continuation line.
- Dont add newlines when dumping the log recorder.

If someone interleaves different log level messages this will go awry,
but really just don't do that.

Cc: Thomas Wood <thomas.wood@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>