pimd: restart the ka timer after the sa adv timer

pimd: restart the ka timer after the sa adv timer

To avoid unnecessary ka activity in the network. When the SA
advertisment timer fires we build SA TLVs and send them to peers. As a
part of this tx we were also restarting the ka timer to avoid
unnecessary ka generation in the next 60 seconds. However because the
adv timer was restarted after tx (i.e. after ka restart) ka timer would
always endup firing just before the adv timer.