Return 202 instead of 200 for "inject_client_cert"

[orenbm]

Connected to #1807

The "inject_client_cert" request initializes the cert injection and then closes the socket. It doesn't wait to see if the cert is injected so it makes more sense to return a 202 Accepted response instead of a 200 OK one.

More info on this can be found here.

DoD:

• The "inject_client_cert" request responds with 202 Accepted upon success