Use context manager for handling G.progress_lock

Manually calling `G.progress_lock.release()` is error-prone as it's not
called when an exception is raised while the lock is acquired.

benchmark/space/draw.py

@@ -77,12 +77,11 @@ def draw_image(filepath, x, y, w, h):
 # Draw.
 
 def benchmark_draw_post_pixel(arg1, arg2):
-    G.progress_lock.acquire()
-    progress_status = G.progress_status
-    result_platform = G.result_platform
-    result_stats = G.result_stats
-    result_dict = G.result_dict
-    G.progress_lock.release()
+    with G.progress_lock:
+        progress_status = G.progress_status
+        result_platform = G.result_platform
+        result_stats = G.result_stats
+        result_dict = G.result_dict
 
     ui_scale = bpy.context.user_preferences.system.ui_scale
     blf.color(font_id, 1.0, 1.0, 1.0, 1.0)