[flang] Fix tests that use the same .mod file

The tests run by `test_any.sh` don't redirect their .mod files to
a different directory so they occasionally fail when the same file
is accessed by different tests at the same time. With locking of
module files implemented, this problem reproduces much more reliably

Work around it by changing the module names to be distinct. Also remove
some comments left over when copied from `test_symbols.sh` tests.

Original-commit: flang-compiler/f18@f7b5c5f0fcbbac4736940761e6d43ec76a3a372a
Reviewed-on: https://github.com/flang-compiler/f18/pull/758