Thank you for that information. After reading your comment I found Oracle Support document,
"Troubleshooting EMCA Failures Due to SYSMAN and Other Existing Objects During Configuration (Doc ID 1110043.1)".
One paragraph in it states,
"When the Database Configuration Assistant (DBCA) is used for creating a database, the DBCA provides an option for the user to choose whether the Enterprise Manager Database Control should be configured in this database. Even if this option is not selected, the DBConsole repository under the SYSMAN schema is still created by the DBCA tool."
That describes what happened to me. DBCA created accounts sysman and mgmt_view, and the DBConsole repository, even though I selected "Configure Enterprise Manager" instead of "Configure Database Control for local management". I will likely use emca to drop these users and remove the repository from the three databases where is is not needed.