Check swift.conf MD5 with recon

I've seen several folks recently have problems with their Swift
clusters because they had different hash prefixes on different
nodes. Let's help them out by having recon check that.

Note that MD5-equality is stronger than what we need (which is
ConfigParser-equality for a particular set of keys), but this way we
don't expose the secret hash prefix and suffix across the internal
network, just the MD5 checksum of the file containing them.

Change-Id: I3af984ee45947345891b3c596a88e3464f178cc7
Load constraints from cluster info dictionary

Use constrainst from the new "swift-constraints" section of test.conf,
fall back to those found in the response to the /info API call,
ultimately falling back to the constraints module's effective
constraints.

Change-Id: Iea01c9c4b5148faa10004a240df411cbe7336a6a
Fix error log of proxy-server when cache middleware is disabled

Change-Id: I0b67721cbb692fb8d2a5dd8b2c4f5383512b7b45
Closes-Bug: #1306591
setting request_node_count doesn't work

Change-Id: Ia161b872cf5ffa43c10334b42cc36d679c3adf56
Fix redundant add operation of set in ring

You don't need to add dev_id into seen_ids again when it has already existed in seen_ids.

Fixes Bug #1311190

Change-Id: If0766de8dc5e2a59a648cae39c789c91131805d2
Merge "Check swift.conf MD5 with recon"
Merge "Load constraints from cluster info dictionary"
Merge "setting request_node_count doesn't work"
Merge "Fix redundant add operation of set in ring"
Merge "Fix error log of proxy-server when cache middleware is disabled"
Fix several typos in the codebase.

These were found using https://github.com/intgr/topy

Change-Id: I0dc7b76c44b8b17b1dcd79184dad1516fb11173c