Camera: Avoid permission check if fallback impl is not enabled

- In connectToProxyLocked, for the case when the vendor proxy service
is supported and the fallback is not, the vendor proxy service will
remain connected to during the check for the fallback impl (or when
useFallback is true, triggered if the vendor impl does not support an
extension). In this case, the permission check should be avoided when
returning to registerClientHelper.

Test: Camera CTS on lynx where vendor proxy is supported and fallback is not; CTS on CF
Bug: 346632129
Change-Id: I826040f582e61339a0df139dc9ce514631af0a6a