MXS-2900 Rename maxtest files

Many of the headers were not renamed to avoid changing every test.

maxscale-system-test/maxtest/src/execute_cmd.cc

@@ -0,0 +1,42 @@
+#include <iostream>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include "execute_cmd.hh"
+
+using namespace std;
+
+
+int execute_cmd(char* cmd, char** res)
+{
+    char* result;
+    FILE* output = popen(cmd, "r");
+    if (output == NULL)
+    {
+        printf("Error opening ssh %s\n", strerror(errno));
+        return -1;
+    }
+    char buffer[10240];
+    size_t rsize = sizeof(buffer);
+    result = (char*)calloc(rsize, sizeof(char));
+
+    while (fgets(buffer, sizeof(buffer), output))
+    {
+        result = (char*)realloc(result, sizeof(buffer) + rsize);
+        rsize += sizeof(buffer);
+        strcat(result, buffer);
+    }
+
+    * res = result;
+
+    int return_code = pclose(output);
+    if (WIFEXITED(return_code))
+    {
+        return WEXITSTATUS(return_code);
+    }
+    else
+    {
+        return -1;
+    }
+}