When doing an ALTER TABLE on a table using partitioning, force the table
  definition to get reloaded, since it may become invalid whenever the ALTER
  TABLE fails (even for an ALTER TABLE without specific partitioning changes).


mysql-test/r/partition.result:
  New results
mysql-test/t/partition.test:
  New regression test
sql/sql_partition.cc:
  Always force table to get reloaded when we ALTER a
  partitioned table