Implemented a caching API to query chunkserver status

[echenj]

The metaserver ping function has been modified to include a caching system. The ping function itself has also been modified to return a Status object instead of modifying the Status passed as a parameter. The cache refresh time is 30 seconds, but will not refresh unless a user asks for data. The added queries will pull information from the cache.
The three new queries are:

• /query/stats/<hostname/ip>
  • Displays all of the attributes for any UpServer instance
• /query/dead/<hostname/ip>
  • Displays the current status of any server, and also the entire disconnect history
• /query/dead/count
  • Displays all of the servers that have any recorded disconnects and their disconnect counts

[comptonqc]

Do any of the query endpoints take parameters?

[echenj]

Looks like the markup got rid of the hostname stuff, I'll add that back into the original post.

[fsareshwala]

Thank you very much for your contribution! It looks like there are some conflicts that need to be resolved here. Can you take a look at resolving those conflicts so that we can review the change and hopefully get it in?