oeqa/runtime/parselogs: improve find call

oeqa/runtime/parselogs: improve find call

getLogList() uses remote find invocations to find the logs. Instead of
relying on shell expansion of wildcards and redundant use of -maxdepth
(pointless as the shell expansion means the find is passed the files to
return), invoke find idiomatically by telling it what directory to
search for and escape the glob so find processes it.

Also remove many pointless str() calls.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>