I saw two test failures in rpl.rpl_gtid_crash where we get this in the error
log:

141123 12:47:54 [Note] InnoDB: Restoring possible half-written data pages 
141123 12:47:54 [Note] InnoDB: from the doublewrite buffer...
InnoDB: Warning: database page corruption or a failed
InnoDB: file read of space 6 page 3.
InnoDB: Trying to recover it from the doublewrite buffer.
141123 12:47:54 [Note] InnoDB: Recovered the page from the doublewrite buffer.

This test case deliberately crashes the server, and if this crash happens
right in the middle of writing a buffer pool page to disk, it is not
unexpected that we can get a half-written page. The page is recovered
correctly from the doublewrite buffer.

So this patch adds a suppression for this warning in the error log for this
test case.