* Redo API client locking
This assigns local values when in critical paths, allowing a single API
client to much more quickly and safely pipeline requests.
Additionally, in order to take that paradigm all the way it changes how
timeouts are set. It now uses a context value set on the request instead
of configuring the timeout in the http client per request, which was
also potentially quite racy.
Trivially tested with
VAULT_CLIENT_TIMEOUT=2 vault write pki/root/generate/internal key_type=rsa key_bits=8192
This should help with transient issues. Full control over min/max delays
and number of retries (and ability to turn off) is provided in the API
and via env vars.
Fix tests.
This allows the same environment variables to be read, parsed, and used
from any API client as was previously handled in the CLI. The CLI now
uses the API environment variable reading capability, then overrides any
values from command line flags, if necessary.
Fixes#618
