Report correct data when multiple volumes are mounted to the same path

We read the data into the iterator from the system, but then recreate
the QStorageInfo object based on the rootPath, and then stat, discarding
the data in the iterator.

We can overwrite the data with the information in the iterator, which
partially fixes the issue. Volume information that can only be retrieved
by stat'ing the root path, such as size information, will only be
correct for one of the entries.

Change-Id: Ie98590876d6a5f525af009f4ff5d595cbc308b3f
Fixes: QTBUG-63209
Reviewed-by: Andrius Štikonas <andrius@stikonas.eu>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qstorageinfo_unix.cpp

@@ -846,6 +846,9 @@ QList<QStorageInfo> QStorageInfoPrivate::mountedVolumes()
 
         const QString mountDir = it.rootPath();
         QStorageInfo info(mountDir);
+        info.d->device = it.device();
+        info.d->fileSystemType = it.fileSystemType();
+        info.d->subvolume = it.subvolume();
         if (info.bytesTotal() == 0)
             continue;
         volumes.append(info);