Typically, in order to revert back to internal user store, you must first delete the current AD connection definition. It's good practice to take a screenshot first in case you need that information later. Once it's deleted, it reverts back to Internal User Store automatically.
If EEM hangs when attempting to revert back to Internal User Store, the changes can be done manually by updating the EEM server.xml file.
To revert back to Internal User Store manually, use the diff example below to update the tags that are different and remove the ones that are not listed for internal user store. Tags that need to be removed <hostname>, <userdn> & <password>. The values for my server.Internal example file are default values.
The following output shows the difference between two server.xml files. One is configured as External User Store and the other as Internal User Store. This shows the lines that need to be updated.
[root@eem-server-mp server]# diff server.External server.Internal
< <genericldapstore name="CA Domain">
< <map>Microsoft Active Directory</map>
< <userdn>cn=prama10,ou=users,ou=north america,dc=ca,dc=com</userdn>
> <internaldirectory name="internaluserstore">
< <security enabled="false">
> <security enabled="true">
Once the changes are made, in order for the changes to take affect the EEM igatewayd service must be restarted.