workloads: Use uninstall method instead of uninstall_executable

For workloads that support Linux targets do not use
`uninstall_executable` as this is not available, instead use `uninstall` as
other targets should be able to determine the appropriate uninstallation
method.

wa/workloads/lmbench/__init__.py

@@ -116,7 +116,7 @@ class Lmbench(Workload):
         context.add_artifact('lmbench-result', "lmbench.output", kind='raw')
 
     def teardown(self, context):
-        self.target.uninstall_executable(self.test)
+        self.target.uninstall(self.test)
 
     #
     # Test setup routines