Correctly set file ownership on startup

[DanielFallon]

[ "$(stat -c %u /vault/config)" != "$(id -u vault)" ] does not correctly test "If the config dir is bind mounted"

This will break if the user starts vault, then copies an additional file into the bind mounted config directory and then restarts the container. While the folder /vault/config will be still owned by vault:vault after the container is restarted, the newly created files will not mirror those permissions unless the sticky bit was set on the directory AND the user didn't inadvertently change them.

The result looks something like this:

Error loading configuration from /vault/config: error loading "/vault/config/local.json": open /vault/config/local.json: permission denied

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[netsandbox]

This would also fix #175

[netsandbox]

@stevendpclark may you can have a look at this?