REGTESTS: fix peers-related regtests regarding "show table"

REGTESTS: fix peers-related regtests regarding "show table"

When I added commit 16b282f4b ("MINOR: stick-table: show the shard
number in each entry's "show table" output"), I don't know how but
I managed to mess up my reg tests since everything worked fine,
most likely by running it on a binary built in the wrong branch.
Several reg tests include some table outputs that were upset by the
new "shard=" field. This test added them and revealed at the same
time that entries learned over peers are not properly initialized,
which will be fixed in a future series of fixes.

This commit requires previous fix "BUG/MINOR: peers: always
initialize the stksess shard value" so as not to trip on entries
learned from peers.