Improve joinPaths

The joinPaths function now correctly joins paths, where the prefix is "/".

Change-Id: I4fb814d732a46e3072ec95fb4dd58f73ffe64c5a
diff --git a/src/utils.cpp b/src/utils.cpp
index 2900e14..9f9fd25 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -9,7 +9,7 @@
 
 std::string joinPaths(const std::string& prefix, const std::string& suffix)
 {
-    if (prefix.empty() || suffix.empty())
+    if (prefix.empty() || suffix.empty() || prefix == "/")
         return prefix + suffix;
     else
         return prefix + '/' + suffix;