core: moved methods out from non static SyncNetworkParametersBuilder

These methods can be used outside from SyncNetworkParametersBuilder,
but in that case their owning class have to be instantiated using
CommandContext parameter, which is completely unrelated to these four
methods.

Change-Id: I8adb975731d8e3a0367585a65993ec53d538fba3
Signed-off-by: Martin Mucha <mmucha@redhat.com>