browse/snapshot_context: Update heuristic selecting default visit type

Check if the visit type can be found in the origin URL first in case an invalid visit type was used when attempting to load the origin.

For instance, the https://svn.wald.intevation.org/edbsilon subversion origin was first attempted to be loaded with a git visit type. As it is in the visit types list, it is the one that is currently selected resulting in a 404 error.