When using IE 11, changes made via the Apache Guacamole admin interface, such as creating or renaming connections, appear to not take effect until after logging out and back in. This is actually due to IE caching the results of the GET requests from the relevant REST API endpoints.
This behavior does not occur in Chrome nor in Firefox and appears to be due to a bug in IE 11's handling of the HTTP cache. Implementations are required to invalidate cached responses for a URI once a PUT, DELETE, or POST request is sent to that same URI:
Adding Cache-Control: no-cache and Pragma: no-cache to requests sent via $http solves the issue.