ipcc: increase restart grace period

ipcc: increase restart grace period

with bad timing and general restart overhead 5 secs were sometimes a
too small timeout, even if it happened really seldom. Increase it a
bit, as it's desired to have the connection stay a live in a lot of
cases, e.g., to not get logged out on pve-cluster update as
pveproxy's verify_ticked couldn't do IPCC.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>