MockBackendUtils.startMockBackend always returns true in native mode

[jamesnetherton]

Bug description

If you do:

export CAMEL_QUARKUS_START_MOCK_BACKEND=false

Then run any native tests (E.g azure-storage-blob & google-storage) where MockBackendUtils.startMockBackend is used at runtime (I.e. in non-test code), you'll find the results aren't as you expect. It's because the result of startMockBackend returns true, regardless of what is set in the environment.

IIRC, a recent(ish) change in Quarkus meant that build time environment variables would not propagate into the native image (since it's a potential security risk).

We should probably avoid this static lookup and just get the config value on each request. The overhead is trivial.