Test: libcrmcommon: Check expectations in mocked getenv()

This allows us to check the argument passed to __wrap_getenv(). If we
don't care, we can always use expect_any().

All our expect_* function choices are here:

• https://api.cmocka.org/group__cmocka__param.html

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>