Prior to this change, configuring a `FixedVersionStrategy` like so
would configure a single "/js/**" path pattern:
```
versionResourceResolver.addFixedVersionStrategy("v1.0.0","/js/**");
```
This commit makes sure that for each path pattern, its prefixed version
is added to the map. For example, the previous configuration also
adds "/v1.0.0/js/**".
Issue: SPR-13883