watchfrr: increase restart timer 20s -> 90s

watchfrr: increase restart timer 20s -> 90s

This commit:
"tools: run `vtysh -b` once for all-startup"

changed things so that `vtysh -b` is run after all daemons have started
up instead of doing it for each daemon as they are started up. This
results in one long `vtysh -b`, which for large configs and many daemons
(in the case I saw, 4 daemons and 30,000 line config) can exceed the 20
second timer watchfrr uses to kill "hung" background tasks.

Shouldn't be any harm to increasing this to 90 seconds to give us some
leeway while still making sure we kill anything truly misbehaving.

Signed-off-by: Quentin Young <qlyoung@nvidia.com>