Handle the downstream_integration_test test arg (#369)

Author: jishnub

test/Aqua.jl test/AquaTest.jltest/Aqua.jl renamed to test/AquaTest.jl

@@ -18,8 +18,13 @@ end
 # Start with autodiscovered tests
 testsuite = find_tests(pwd())
 
+if "--downstream_integration_test" in ARGS
+    delete!(testsuite, "AquaTest")
+end
+filtered_args = filter(!=("--downstream_integration_test"), ARGS)
+
 # Parse arguments
-args = parse_args(ARGS)
+args = parse_args(filtered_args)
 
 if filter_tests!(testsuite, args)
     delete!(testsuite, "testutils")