HBASE-4271 Clean up coprocessor's handlings of table operations
Review Request #1691 - Created Sept. 1, 2011 and updated
Along with coprocessor work, also fix HBaseAdmin.deleteTable so that it waits until the table is removed from HMaster's HTableDescriptor list. 1. Fix preCreateTable, postCreateTable, preAssign, postAssign, preUnassign APIs. 2. Make coprocessor honor bypass request from preMove, preAddColumn, preModifyColumn, preDeleteColumn.