cache availability of FES across app session

[tomholub]

This calls the FES one extra time before each request - which is excessive. Ok for now since it works, but in the future we should cache a boolean to mark whether FES is available or not. I'll file a separate issue.

Originally posted by @tomholub in #1261 (comment)

[tomholub]

[tomholub]

This issue, as originally defined, was I think fixed in #1467

However, It would be even better if this was checked only once per app startup (I think now it's once per class init. which may be only on app startup. so maybe we already did it). It would be for Roma to have a look at, later.