Restrict file permissions for config file/dir
Restrict file permissions for config file/dir

Velero client config file should have restricted file permissions to be
read/write-able for the user that creates it--similiar to files like
`.ssh/id_rsa`

Refer to OTG-CONFIG-009: Test File Permission
> Impoper file permission configuration may result in privilledge
escalation, information explousure, DLL injection, or unauthorized file
access.
Therefore, files permission must be properly configured with minium
access permission by default.

[source](https://www.owasp.org/index.php/Test_File_Permission_(OTG-CONFIG-009))

Ticket: #1758
Signed-off-by: John Naulty <eb5b6d92b6c73fdbcbd6fae268cc5dfe57c50c7e@bitgo.com>

heptio/ark,heptio/ark