configure: Don't mix glib and libcheck tests

test-coroutine is listed as a libcheck test in the 'checks' variable. This
is not right because 'make check' won't run test-coroutine if libcheck
tests are not enabled (either because libcheck isn't detected or because
--disable-check-utests is passed).

Tests using the glib test framework are independent from libcheck and
afaik are always present (although having a configure switch to disable
them is probably worth it).

Untangle test-coroutine from the libcheck tests by introducing the
'test_progs' variable and using it to generate the test list used by
'make check'.

Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
