API-4316 fix db2 hang on passenger process spawn

See the work found here: https://github.fbsdata.com/gist/wade/dfd89b945dcc391c6d4cbb70ca3b688a

Author: wlmcewen

lib/octopus/proxy.rb

@@ -328,6 +328,7 @@ def send_queries_to_slave_group(method, *args, &block)
     # Ensure that a single failing slave doesn't take down the entire application
     def with_each_healthy_shard
       @shards.each do |shard_name, v|
+        next if shard_name.to_s == "master"
         begin
           yield(v)
         rescue => e