MXS-2243 System tests brings VMs by themselves (#193)

maxscale-system-test changed in order to control test environment by itself.
Every test checks which machines are running, compare with list of needed machines
and start new VMs is they are missing in the running machines list.
Tests are executiong MDBCI commands, MDBCI executable should be in the PATH

maxscale-system-test/envv.cpp

@@ -0,0 +1,61 @@
+#include <string.h>
+#include <string>
+#include "envv.h"
+
+char * readenv(const char * name, const char *format, ...)
+{
+    char * env = getenv(name);
+    if (!env)
+    {
+        va_list valist;
+
+        va_start(valist, format);
+        int message_len = vsnprintf(NULL, 0, format, valist);
+        va_end(valist);
+
+        if (message_len < 0)
+        {
+            return NULL;
+        }
+
+        env = (char*)malloc(message_len + 1);
+
+        va_start(valist, format);
+        vsnprintf(env, message_len + 1, format, valist);
+        va_end(valist);
+        setenv(name, env, 1);
+    }
+    return env;
+}
+
+int readenv_int(const char * name, int def)
+{
+    int x;
+    char * env = getenv(name);
+    if (env)
+    {
+        sscanf(env, "%d", &x);
+    }
+    else
+    {
+        x = def;
+        setenv(name, (std::to_string(x).c_str()), 1);
+    }
+    return x;
+}
+
+bool readenv_bool(const char * name, bool def)
+{
+    char * env = getenv(name);
+    if (env)
+    {
+        return ((strcasecmp(env, "yes") == 0) ||
+                (strcasecmp(env, "y") == 0) ||
+                (strcasecmp(env, "true") == 0));
+    }
+    else
+    {
+        setenv(name, def ? "true" : "false", 1);
+        return def;
+    }
+}