Try add-user.sh --help
You will find the -sc and -dc option to set the directories
add-user.sh --help does not work for me (I tried with 7.1.1.Final and 7.1.0.Final), it does not show any help message:
What type of user do you wish to add?
a) Management User (mgmt-users.properties)
b) Application User (application-users.properties)
I also tried
$JBOSS_HOME/bin/add-user.sh -sc /xyz/standalone/ -dc /xyz/domain/
but add-user.sh wrote mgmt-users.properties below $JBOSS_HOME
The issue that you are looking for related to the location overrides is AS7-3995, this will be in a community release once the AS 7.2.x releases start - alternatively you could build the AS 7.1.2.Final tag yourself to obtain this change.