Add tests from develop

Added tests from develop. The test results need to be modified for 2.0.

maxscale-system-test/execute_cmd.h

@@ -0,0 +1,17 @@
+#ifndef EXECUTE_CMD_H
+#define EXECUTE_CMD_H
+
+#include <iostream>
+#include <unistd.h>
+
+using namespace std;
+
+/**
+ * @brief execute_cmd Execute shell command
+ * @param cmd Command line
+ * @param res Pointer to variable that will contain command console output (stdout)
+ * @return Process exit code
+ */
+int execute_cmd(char * cmd, char ** res);
+
+#endif // EXECUTE_CMD_H