pimd: Fix missing pimreg interface

`pimregX` of specific vrf can be deleted from kernel after this vrf is
deleted.  However, then `pimdregX` will never come back to kernel after
adding it ( the same vrf ) back.  That is to say, it exists only in
daemon, but not in kernel.

The root cause is this `pimregX` is not really deleted for its `configured`
flag.  `pim_if_create_pimreg()` will reuse it, so it will never be added
into kernel again.

Just remove the `configured` flag of `pimregX`, allow its deletion.

Fixes #13454

Signed-off-by: anlan_cs <[email protected]>

pimd/pim_iface.c

@@ -1498,14 +1498,6 @@ void pim_if_create_pimreg(struct pim_instance *pim)
 		if (!pim->regiface->info)
 			pim_if_new(pim->regiface, false, false, true,
 				   false /*vxlan_term*/);
-
-		/*
-		 * On vrf moves we delete the interface if there
-		 * is nothing going on with it.  We cannot have
-		 * the pimregiface deleted.
-		 */
-		pim->regiface->configured = true;
-
 	}
 }