live: umount all partitions before partition setup

If new partition layout is specified, unmount cache and any other partition
under /mnt.

src/live/ogOperations.py

@@ -312,6 +312,9 @@ class OgLiveOperations:
         self._ogbrowser_clear_logs()
         self._restartBrowser(self._url_log)
 
+        umount_all()
+        umount_cache()
+
         diskname = get_disks()[int(disk)-1]
         cxt = fdisk.Context(f'/dev/{diskname}',
                             details=True)
@@ -331,8 +334,6 @@ class OgLiveOperations:
                 continue
             if ogRest.terminated:
                 break
-            if part["code"] == 'CACHE':
-                umount_cache()
 
             pa = fdisk.Partition(start_follow_default=True,
                                  end_follow_default=False,