Avoid NameError when Lock is used in place of LuaLock (#231)

* Update agent.py

* Update worker.py

Author: deveil

mrq/agent.py

@@ -12,7 +12,8 @@
 try:
     from redis.lock import LuaLock
 except ImportError:
-    from redis.lock import Lock
+    # Change name to avoid NameError raised when use of LuaLock at line 147
+    from redis.lock import Lock as LuaLock
 
 from .processes import Process, ProcessPool
 from .utils import MovingETA, normalize_command

mrq/worker.py

@@ -19,7 +19,8 @@
 try:
     from redis.lock import LuaLock
 except ImportError:
-    from redis.lock import Lock
+    # Change name to avoid NameError raised when use of LuaLock at line 151
+    from redis.lock import Lock as LuaLock
 
 from collections import defaultdict
 from mrq.utils import load_class_by_path