pimd: Add 'test pim keepalive-reset A.B.C.D A.B.C.D' command

pimd: Add 'test pim keepalive-reset A.B.C.D A.B.C.D' command

Add a test command to pim that allows you to reset the keepalive timer
for an upstream to it's max value.  This is to allow purposeful testing
of cleanup code in pim, by forcing the keeaplive timer to expire later.

robot# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
enp3s0    192.168.201.136 225.1.0.0       NotJ,RegP   00:00:10 00:00:52  00:00:25  00:02:54       1
robot# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
enp3s0    192.168.201.136 225.1.0.0       NotJ,RegP   00:00:11 00:00:51  00:00:24  00:02:53       1
robot# test pim keep 192.168.201.136 225.1.0.0
Setting (192.168.201.136,225.1.0.0) to current keep alive time: 210
robot# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
enp3s0    192.168.201.136 225.1.0.0       NotJ,RegP   00:00:27 00:00:35  00:00:08  00:03:27       1
robot#

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>