workloads/dhrystone: do initialize/finalize once per run

Add in the "once" decorator for the initialize and finalize methods to
ensure that they only run once per run.

wa/workloads/dhrystone/__init__.py

@@ -19,6 +19,7 @@ import os
 import re
 
 from wa import Workload, Parameter, ConfigError, Executable
+from wa.utils.exec_control import once
 
 
 class Dhrystone(Workload):
@@ -71,6 +72,7 @@ class Dhrystone(Workload):
                   '''),
     ]
 
+    @once
     def initialize(self, context):
         resource = Executable(self, self.target.abi, 'dhrystone')
         host_exe = context.resolver.get(resource)
@@ -143,6 +145,7 @@ class Dhrystone(Workload):
         context.add_metric('total DMIPS', total_dmips)
         context.add_metric('total score', total_score)
 
+    @once
     def finalize(self, context):
         self.target.uninstall('dhrystone')