Support HDFS in Vault Agent Auto-Auth File Sink

[gabrieljones]

Is your feature request related to a problem? Please describe.
HDFS does not like the way agent updates the token file. ie overwrite by rename
eg HDFS does not like

> touch token_file
> touch new_token_file
> mv new_token_file token_file 
mv: cannot move ‘new_token_file’ to ‘token_file’: Input/output error

Describe the solution you'd like
sink should have an option to delete the existing token file before writing the new token to the same path

Describe alternatives you've considered
HDFS is not an ideal place to put tokens but in our case its the only volume shared by all the nodes that need the token