test: Do not create data directory for memory databases (#7323)

Co-authored-by: Bart <11445373+bthomee@users.noreply.github.com>

src/xrpld/app/misc/SHAMapStoreImp.cpp

@@ -387,8 +387,12 @@ void
 SHAMapStoreImp::dbPaths()
 {
     Section const section{app_.config().section(Sections::kNodeDatabase)};
-    boost::filesystem::path dbPath = get(section, Keys::kPath);
 
+    // Skip creating the directory when an in-memory database is used.
+    if (boost::iequals(get(section, Keys::kType), "memory"))
+        return;
+
+    boost::filesystem::path dbPath = get(section, Keys::kPath);
     if (boost::filesystem::exists(dbPath))
     {
         if (!boost::filesystem::is_directory(dbPath))