Fix the inconsistent permission checks for bulkloading.

Three checks(prePrepareBulkLoad, preCleanupBulkLoad, preBulkLoadHFile) are being done while performing secure bulk load, and it looks the former two checks for 'W', while the later checks for 'C'. After having offline chat with jdcryans, looks like the inconsistency among checks were unintended. So, we can address this multiple ways.

• All checks should be for 'W'
• All checks should be for 'C'
• All checks should be for both 'W' and 'C'
  Posting the initial patch going by the first option. Open to discussion.