Allowing multiple users to access the /tmp/ray file at the same time (#3591)

* Allowing multiple users to access the /tmp/ray file at the same time

Previous sequence that caused this issue:
* User A starts ray with `ray.init` when /tmp/ray does not exist
* User B starts ray with `ray.init` and /tmp/ray now exists

User B will get a permissions error
Checking the permissions, /tmp/ray is 700

I have identified a race condition in `try_to_create_directory`
* Multiple processes try to create /tmp/ray at the same time
* chmod is either silently erroring or working properly within the race condition

Resolution: Move chmod outside of the check for whether the directory exists or not.

* Adding try except for users who do not own the directory

python/ray/tempfile_services.py

@@ -64,7 +64,10 @@ def try_to_create_directory(directory_path):
                 "exists.".format(directory_path))
         # Change the log directory permissions so others can use it. This is
         # important when multiple people are using the same machine.
+    try:
         os.chmod(directory_path, 0o0777)
+    except PermissionError:
+        pass
 
 
 def get_temp_root():