oeqa/logparser: Fix performance issues with ptest log parsing
On the autobuilder a ptest log with 2.1 million lines took around 18 hours to
process. This is clearly crazy.
We can tweak the processing code to:
a) Stop repeatedly joining large strings together (append to a list instead)
b) Use one startswith expression instead of multiple re.search() operations
With this change it takes 18 hours down to around 12s.
[YOCTO #13696]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
