odhcp6c: sync and accumulate RA & DHCPv6 events as fast as possible

odhcp6c: sync and accumulate RA & DHCPv6 events as fast as possible

This fixes commit dc186d6d2b0d which introduced accumulation delay
differences between the 2 possible scenarios:
  1. When DHCPv6 bound event precede RA receival, sync script is called
     after 1 second since accumulation has been completed (i.e. RA has
     been received).
  2. When RA receival precedes DHCPv6 bound event, sync script is called
     after a delay of 10 seconds since accumulation is done.

Fixes: dc186d6d2b0d ("odhcp6c: sync and accumulate RA & DHCPv6 events correctly")
Signed-off-by: Alin Nastac <[email protected]>
Link: https://github.com/openwrt/odhcp6c/pull/82
Signed-off-by: Álvaro Fernández Rojas <[email protected]>