tests: Fix problem with test running

Tests were not allowed to be ran, the following
issues were fixed:
    - creating the results folder before test running
    - sudo $PREFIX moved before variables definition which
        allow to pass them through the sudo to test script.
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

testsuite/Makefile

 ## -- Config --
 DEV := lo
-PREFIX := sudo
+PREFIX := sudo -E
+RESULTS_DIR := results
 ## -- End Config --
 
 TESTS := $(patsubst tests/%,%,$(wildcard tests/*.t))
@@ -23,23 +24,24 @@ listtests:
 alltests: $(TESTS)
 
 clean:
-	@rm -rf results/*
+	@rm -rf $(RESULTS_DIR)
 
 distclean: clean
 	echo "Entering iproute2" && cd iproute2 && $(MAKE) distclean && cd ..;
 
 $(TESTS):
+	@mkdir -p $(RESULTS_DIR)
 	@for i in $(IPVERS); do \
 		o=`echo $$i | sed -e 's/iproute2\///'`; \
 		echo -n "Running $@ [$$o/`uname -r`]: "; \
 		TC="$$i/tc/tc" IP="$$i/ip/ip" DEV="$(DEV)" IPVER="$@" SNAME="$$i" \
-		ERRF="results/$@.$$o.err" $(KENV) $(PREFIX) tests/$@ > results/$@.$$o.out; \
+		ERRF="$(RESULTS_DIR)/$@.$$o.err" $(KENV) $(PREFIX) tests/$@ > $(RESULTS_DIR)/$@.$$o.out; \
 		if [ "$$?" = "127" ]; then \
 			echo "SKIPPED"; \
-		elif [ -e "results/$@.$$o.err" ]; then \
+		elif [ -e "$(RESULTS_DIR)/$@.$$o.err" ]; then \
 			echo "FAILED"; \
 		else \
 			echo "PASS"; \
 		fi; \
-		dmesg > results/$@.$$o.dmesg; \
+		dmesg > $(RESULTS_DIR)/$@.$$o.dmesg; \
 	done