lib: Correct valgrind errors

lib: Correct valgrind errors

In CSPF topo test, valgrind detects uninitialized bytes when exporting TE
Opaque information through ZEBRA. This is due to C pragma compilation directive
__attribute__(aligned(8)) in struct ls_node_id in link_state.h. Valgrind
consideris that struct ls_node_id nid = {} doesn't initialized the padding
bytes introduced by gcc.

This patch simply removes the C pragma compilation directive and also takes
opportunity to remove the transmission of remote node id for vertices and
subnets which is not known. Indeed, remote node id is only pertinent for
edges.

Signed-off-by: Olivier Dugeon <olivier.dugeon@orange.com>