Bug 8444 - Persistent prefix-based shard cannot load its snapshot

Since the name is URL-encoded, we have to make sure it does not get
double-encoded -- hence we need to make a pass of URL-decoding before
we use the result.

Change-Id: I20fe8702ad7e405a8b68d8bda2f9ce4522f2dfd0
Signed-off-by: Jakub Morvay <jmorvay@cisco.com>