network: Convert to virErrorRestore/virErrorPreserveLast
network: Convert to virErrorRestore/virErrorPreserveLast

Replaced usage of virSaveLastError and virSetError/virFreeError with
virErrorPreserveLast and virErrorRestore respectively.

Signed-off-by: Syed Humaid <8022e082a51c23b826b89c93f82078eb386329fb@gmail.com>

andreabolognani/libvirt,libvirt/libvirt,olafhering/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,olafhering/libvirt,fabianfreyer/libvirt,eskultety/libvirt,andreabolognani/libvirt,jfehlig/libvirt,crobinso/libvirt,eskultety/libvirt,eskultety/libvirt,jardasgit/libvirt,andreabolognani/libvirt,zippy2/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,jardasgit/libvirt,libvirt/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,crobinso/libvirt,olafhering/libvirt,andreabolognani/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,eskultety/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,eskultety/libvirt