(QENG-1906) Refactor initialize to allow config passing

Prior to this commit, several pieces of vmpooler performed configuration
and initialization steps within 'initialize'. This made it difficult to
pass in mock objects for testing purposes.

This commit performs a single configuration and passes the results to
the various pieces of vmpooler.

lib/vmpooler/api.rb

@@ -1,24 +1,7 @@
 module Vmpooler
   class API < Sinatra::Base
     def initialize
-      # Load the configuration file
-      config_file = File.expand_path('vmpooler.yaml')
-      $config = YAML.load_file(config_file)
-
-      $config[:uptime] = Time.now
-
-      # Set some defaults
-      $config[:redis] ||= {}
-      $config[:redis]['server'] ||= 'localhost'
-
-      if $config[:graphite]['server']
-        $config[:graphite]['prefix'] ||= 'vmpooler'
-      end
-
-      # Connect to Redis
-      $redis = Redis.new(host: $config[:redis]['server'])
-
-      super()
+      super
     end
 
     set :environment, :production
@@ -51,8 +34,14 @@ module Vmpooler
     use Vmpooler::API::Reroute
     use Vmpooler::API::V1
 
-    Thread.new do
-      run!
+    def configure(config, redis, environment = :production)
+      self.settings.set :config, config
+      self.settings.set :redis, redis
+      self.settings.set :environment, environment
+    end
+
+    def execute!
+      self.settings.run!
     end
   end
 end