MINOR: stick-table: show the shard number in each entry's "show table" output

Stick-tables support sharding to multiple peers but there was no way to
know to what shard an entry was going to be sent. Let's display this in
the "show table" output to ease debugging.

doc/management.txt

@@ -3544,6 +3544,16 @@ show table <name> [ data.<type> <operator> <value> [data.<type> ...]] | [ key <k
           | fgrep 'key=' | cut -d' ' -f2 | cut -d= -f2 > abusers-ip.txt
           ( or | awk '/key/{ print a[split($2,a,"=")]; }' )
 
+  When the stick-table is synchronized to a peers section supporting sharding,
+  the shard number will be displayed for each key (otherwise '0' is reported).
+  This allows to know which peers will receive this key.
+  Example:
+        $ echo "show table http_proxy" | socat stdio /tmp/sock1 | fgrep shard=
+          0x7f23b0c822a8: key=10.0.0.2 use=0 exp=296398 shard=9 gpc0=0
+          0x7f23a063f948: key=10.0.0.6 use=0 exp=296075 shard=12 gpc0=0
+          0x7f23b03920b8: key=10.0.0.8 use=0 exp=296766 shard=1 gpc0=0
+          0x7f23a43c09e8: key=10.0.0.12 use=0 exp=295368 shard=8 gpc0=0
+
 show tasks
   Dumps the number of tasks currently in the run queue, with the number of
   occurrences for each function, and their average latency when it's known

src/stick_table.c

@@ -4456,7 +4456,7 @@ static int table_dump_entry_to_buffer(struct buffer *msg,
 		dump_binary(msg, (const char *)entry->key.key, t->key_size);
 	}
 
-	chunk_appendf(msg, " use=%d exp=%d", entry->ref_cnt - 1, tick_remain(now_ms, entry->expire));
+	chunk_appendf(msg, " use=%d exp=%d shard=%d", entry->ref_cnt - 1, tick_remain(now_ms, entry->expire), entry->shard);
 
 	for (dt = 0; dt < STKTABLE_DATA_TYPES; dt++) {
 		void *ptr;