If any E2E test hangs, it'll eventually timeout and panic, causing the
all the remaining tests to fail. External commands should use a short
context whenever possible so we can fail the test quickly and move on
to the next test.
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.
