Generated server url computation not cleared

[antechrestos]

Similar to #1712 , server url automatically generated mixed with customizer that modifies automatically generated server list, when used with both direct and reversed proxy (say with different context time for the same runtime), we end with a first asked wins as, at first call, open api is built and

• server url gets computed
• server list gets copied (strange to use json serialisation)
• customizer are called
• As server list is modified by customizer, it is considered that server are provided.

The last assumption is wrong as if it was not provided at first.

In the end we ends with a customized generated server put in cache.

[antechrestos]

Moreover, if find that putting some data that are linked to the current call (generated url) as an attribute of a spring bean (singleton) is quite a source of trouble