HPCC-10833 Errors adding ESP user not being handled consistently

When adding users, some errors cause a log message and an error return
code, leaving the partially created account, which other errors throw
exceptions, which activates the logic to clean up and delete the account.

This fix changes the error returns to exceptions, which will clean up
properly, and display the failure

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>