Bug 1059814 - Deploy script: Remove unnecessary sys.path additions

The directory of the currently running script is already on the path:
https://docs.python.org/2/tutorial/modules.html#the-module-search-path
...so adding it is unnecessary.

In addition, I don't believe we need the treeherder-service directory on
the path, since we don't directly import anything from there.

deployment/update/update.py

@@ -11,9 +11,6 @@ Requires commander_ which is installed on the systems that need it.
 """
 
 import os
-import sys
-
-sys.path.append(os.path.dirname(os.path.abspath(__file__)))
 
 from commander.deploy import task, hostgroups
 import commander_settings as settings
@@ -21,8 +18,6 @@ import commander_settings as settings
 th_service_src = os.path.join(settings.SRC_DIR, 'treeherder-service')
 th_ui_src = os.path.join(settings.SRC_DIR, 'treeherder-ui')
 
-sys.path.append(th_service_src)
-
 is_prod = 'treeherder.mozilla.org' in settings.SRC_DIR
 env_flag = '-p' if is_prod else '-s'