pgsql: Fix a couple of error-handling bugs in the xlogreader patch.

Fix a couple of error-handling bugs in the xlogreader patch.

XLogReadRecord should reset its state on every error, to make sure it
re-reads the page on next call. It was inconsistent in that some errors did
that, but some did not.

In ReadRecord(), don't give up on an error if we're in standby mode. The
loop was set up to retry, but the checks within the loop broke out of the
loop on any error.

Andres Freund, with some tweaking by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/1296d5c53cad26c775993d6c29e1311919202638

Modified Files
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src/backend/access/transam/xlog.c | 31 +++++++++++++++++++++----------
src/backend/access/transam/xlogreader.c | 30 +++++++-----------------------
2 files changed, 28 insertions(+), 33 deletions(-)