sharding: Let swift-manage-shard-ranges accept a relative path

Previously, passing a relative path would confuse the ContainerBroker about
which DB files are available, leading to an IndexError when none were found.

Just call realpath() on whatever the user provided so we don't have to muck
with any of the broker code.

Change-Id: Icdf100dfcd006d975b49d151b99aa9272452d013

swift/cli/manage_shard_ranges.py

@@ -158,6 +158,7 @@ All three steps may be performed with one sub-command::
 from __future__ import print_function
 import argparse
 import json
+import os.path
 import sys
 import time
 
@@ -513,8 +514,8 @@ def main(args=None):
         print('\nA sub-command is required.')
         return 1
     logger = get_logger({}, name='ContainerBroker', log_to_console=True)
-    broker = ContainerBroker(args.container_db, logger=logger,
-                             skip_commits=True)
+    broker = ContainerBroker(os.path.realpath(args.container_db),
+                             logger=logger, skip_commits=True)
     try:
         broker.get_info()
     except Exception as exc: