[general] Allow default wait_for interval to be overiden globally.

lib/fog/core.rb

@@ -20,6 +20,7 @@ require 'fog/core/current_machine'
 require 'fog/core/deprecation'
 require 'fog/core/errors'
 require 'fog/core/hmac'
+require 'fog/core/interval'
 require 'fog/core/logger'
 require 'fog/core/model'
 require 'fog/core/mock'

lib/fog/core/interval.rb

@@ -0,0 +1,11 @@
+module Fog
+  @interval = 1
+  def self.interval
+    @interval
+  end
+
+  def self.interval=(interval)
+    raise ArgumentError, "interval must be non-negative" unless interval >= 0
+    @interval = interval
+  end
+end

lib/fog/core/wait_for.rb

@@ -1,5 +1,5 @@
 module Fog
-  def self.wait_for(timeout=Fog.timeout, interval=1, &block)
+  def self.wait_for(timeout=Fog.timeout, interval=Fog.interval, &block)
     duration = 0
     start = Time.now
     until yield || duration > timeout