[ldap] auth method fix request_timeout

[fairclothjm]

Description

This PR fixes a bug where the LDAP auth method does not implement the request_timeout configuration parameter, neither storing it, nor enforcing it for connections made to an LDAP server.

[fairclothjm]

Manual Tests

Setup

First, navigate to the vault directory and build this branch for docker:

git checkout ldap-request-timeout
make docker-dev

Next, from the vault-tools directory on your machine checkout the ldap-local-docker-dev branch:

git checkout ldap-local-docker-dev
cd users/jodonnell/ldap-auth-example

Next, run the startup script with the dev argument which will use the docker image built in the first step:

./run.sh dev

Export env vars:

export VAULT_ADDR="http://localhost:8200"
export VAULT_TOKEN="root"

Test

vault auth enable ldap
vault read auth/ldap/config # request_timeout is 90, the default
vault write auth/ldap/config timeout_request=29
vault read auth/ldap/config # request_timeout is 29

[calvn]

Couple of small comments, but looking good! PasswordlessMap() is called on config read, so I think that we were always storing request_timeout, just not returning it back.