Increase the timeout for vaultsecrets. As the default interval is 0.1s, 10
retries mean it only retries for one second, a very short time for some waiting
scenarios in the test (e.g. starting allocs, etc).
The `$NOMAD_SECRETS_DIR` environment variable is rendered as `/secrets`, which
prior to the recent security patch would unintentionally escape the file
sandbox and get dropped in a directory named `/secrets` where the Nomad client
binary was running. The `VaultSecrets` test was accidentally relying on this
behavior and that causes the test to fail.
