Fix more bad member swap definitions in unordered_map.

The __unordered_map_equal and __unordered_map_hash wrappers
attempt to swap const qualified predicates whenever the predicate
is empty, and is subject to the EBO.

Swapping const values seems blatently incorrect. This patch removes
the const qualifier so the values are swapped as non-const.

llvm-svn: 300154