Fix tags on parallel interface when in LS discretization mode - for ParMmg

[laetitia-m]

In ParMmg and in LS discretization mode, when we arrive for the second time in MMG5_bdryTria, in the surface analysis, xtetra.tag exists and tria.tag is updated using xtretra values.

In MMG5_bdryTria, the edge tags of the triangle are assigned based on what is stored in xtetra.tag. However, in parallel, th edges should not inherit:
(1) the tag PARBDYBDY here and
(2) the tags PARBDY, NOSURF and REQ when we arrive from a non-parallel faces.
The assignment of these appropriate tags is done later in MMG5_mmgHashTria

[Algiane]

I would add some additionnal comments to illustrate the issue we found when analysing for the second time the surface intersections in ParMmg :

/* Assign tags to tria from xtetra->tag and remove redundant boundary tag: when called from ParMmg in ls mode, it is needed to remove the parallel tags coming from previous surface analysis to ensure the suitable setting of the MG_BDY tag along edges at the intersection between geometrical (true) boundaries and purely parallel interfaces. For that, it is mandatory to remove the MG_PARBDYBDY tag already added along such edges (see the step 2 of the mmgHashTria implementation) */

[Algiane]

Thanks!