Re-sync the text in v2 and v3 help and the docs
Depends-On: If4ac5356ade8cff347bb9eb9f88d1ace82bb7275
Change-Id: Iabef2f271fcf46748295c29713fea1811dcab29c
A follow up work item from I52ff2020ef2fcbdc8a98280b73c6fd4a93bc8e0f
to support domain scoped users and projects for ec2creds in the
v3 identity api.
Related-Bug: 1236326
Change-Id: If4ac5356ade8cff347bb9eb9f88d1ace82bb7275