Rationalize Link Parameters flags

Rationalize Link Parameters flags

 * lib/if.h: Remove LP_TE as Link Parameters is set if different from 0
See IS_LINK_PARAMS_SET macro and use LP_TE_METRIC to determine if TE metric
is set or not
 * lib/if.c: replace LP_TE by LP_TE_METRIC in default LP status
 * zebra/interface.c: replace LP_TE by LP_TE_METRIC and check if TE metric
is equal to standard metric or not
 * ospfd/ospf_te.c: replace LP_TE by LP_TE_METRIC
 * isisd/isis_te.c: replace LP_TE by LP_TE_METRIC

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