Fix crash on exit with --debug and PGCOPYDB_LOG_FILENAME (#589)

We close the FILE which is used to log into file before calling
the `copydb_cleanup_sysv_resources` which still uses log functions leads
to crash due to invalid FILE* access.

This commit fixes the crash by closing the FILE after calling the
cleanup function.

Signed-off-by: Arunprasad Rajkumar <ar.arunprasad@gmail.com>