bgpd: avoid heap fragmentation in bgp_clear_route_table

bgpd: avoid heap fragmentation in bgp_clear_route_table

In bgp_clear_route_table, moved cleanup code before the allocation
of the work queue items. This returns the memory to the system
allocator before allocating new and might therefore help avoiding
heap fragmentation.

* bgp_route.c: (bgp_clear_route_table) moved code blocks.

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Reviewed-by: Leonid Rosenboim <Leonid.Rosenboim@windriver.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>