oeqa/utils/decorators: LogResults fix race condition in linkfile

oeqa/utils/decorators: LogResults fix race condition in linkfile

In order to avoid race condition when test if exists the linkfile
use bb.utils.lock, the best solution is to create a unique name
for the link file.

There is no way to create a unique linkfile name at this decorator
because is needed the machine and image variables, those variables
can't be passed easily in this code.

To avoid broke test export functionality use a try/except because bb
isn't available when use test export

[YOCTO #10225]

(From OE-Core rev: 059d475b6bce1e5414170a4fe2e7989f6b0eacd6)

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>