I've continued to observe two prompts for the master password each time icedove starts
I removed the SOGo Connector[1] plugin from icedove and restarted and the master password prompt is only appearing once now. This leads me to suspect there is something going wrong in the way plugins initialize when they need to use stored credentials. The SOGo Connector stores credentials for access to a CardDAV address book URL. 1. https://sogo.nu/files/docs/SOGo%20Mozilla%20Thunderbird%20Configuration.pdf
