virStorageFileGetMetadataRecurse: Remove impossible error report
virStorageFileGetMetadataRecurse: Remove impossible error report

We call virStorageFileSupportsBackingChainTraversal which already checks
that the 'storageFileRead' callback is non-NULL, which in turn means
that virStorageFileRead will not return -2.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

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