[flang] Added tests for image control statements in DO CONCURRENT

There was already code in check-do.cc to test for the presence of a
variety of different image control statements, but several of them did
not have associated tests.  This change adds tests for most of them.

Also, I removed the check for the END PROGRAM statement, since its
presence causes a syntax error which prevents the semantic check from
ever being reached.

Original-commit: flang-compiler/f18@9cc6f5bd40689fa4bd0972e821ad3a871733b6fb
Reviewed-on: https://github.com/flang-compiler/f18/pull/764