Remove if Butler exists checks from bin.src scripts.

Checks are made against local filesystem only. This stopped
being a valid assumption since S3Datastore was implemented
as the data repository does not need to be local anymore.

The failure case should be handled internaly by Butler itself
at instantiation time.

bin.src/makeGen3DcrSubfilters.py

@@ -35,11 +35,6 @@
 
 args = parser.parse_args()
 
-# Verify any supplied paths actually exist on disk
-if not os.path.exists(args.butler):
-    print("Butler path specified does not exists")
-    sys.exit(1)
-
 config = MakeGen3DcrSubfiltersConfig()
 if args.configFile:
     if not os.path.exists(args.configFile):

bin.src/makeGen3Skymap.py

@@ -37,11 +37,6 @@
 
 args = parser.parse_args()
 
-# Verify any supplied paths actually exist on disk
-if not os.path.exists(args.butler):
-    print("Butler path specified does not exists")
-    sys.exit(1)
-
 config = MakeGen3SkyMapConfig()
 if args.configFile:
     if not os.path.exists(args.configFile):