pgsql: Cancel pending fsync requests during WAL replay of DROP DATABASE,

Log Message:
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Cancel pending fsync requests during WAL replay of DROP DATABASE, per bug
report from David Darville.  Back-patch as far as 8.1, which may or may not
have the problem but it seems a safe change anyway.

Tags:
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REL8_1_STABLE

Modified Files:
--------------
    pgsql/src/backend/commands:
        dbcommands.c (r1.173.2.2 -> r1.173.2.3)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/dbcommands.c.diff?r1=1.173.2.2&r2=1.173.2.3)