sanitycheck: all handlers produce the same log now

Rather than having handler generate differently named log files,
generate the same for all handlers, so qemu, native and unit will now
generate handler.log.

This will simplify things and reporting will be consistent.  Also, this
fixes a bug where we only included qemu.log in generated reports.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>