tests: Add runtime generated files to .gitignore

When make tests then 2 folders are generated:

    testsuite/results
    testsuite/iproute2/iproute2-this
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

.gitignore

@@ -31,3 +31,7 @@ series
 .gdbinit
 .gdb_history
 *.gdb
+
+# tests
+testsuite/results
+testsuite/iproute2/iproute2-this