More than one QNetworkAccessManager in same process on Symbian does not work properly

The current issue is that the whole bearer management on Symbian bases on a per-process
POSIX layer (OpenC) functionality. If there are multiple entities (QNAMs) within the same process controlling the same setting without 'cooperatively synchronizing', there will be conflicts.

To be able to fix this properly, we need to be able to control interfaces per socket, rather than per process --> this means that the symbian native socket migration needs to be in place (QTBUG-7274).
(There was an attempt to fix this with current existing OpenC ioctls, but they resulted in extra connection selection UI queries displayed to user)