Implement forcelocal in AIX providers

Currently, the forcelocal attribute on user and group resources only works on Linux based systems where libuser is available. However, other operating systems, such as AIX, would also benefit from having user and group resources prevented from reaching out to LDAP or AD backends. This causes problems primarily when a user or group resource is applied when there is a user or group with the same name in the backend database. The provider will error out, and the agent run will fail.

AIX does provide the "-R files" flag for many of its user and group management commands. It may be possible to leverage this to implement a forcelocal option without the presence of libuser.