telemetry: fix empty JSON dictionaries

[ upstream commit 324ec1df541711ca829f4d99b7e2d32ffe38d3ca ]

Fix to allow telemetry to handle empty dictionaries correctly.

This patch resolves an issue where empty dictionaries are reported
by telemetry as '[]' rather than '{}'. Initializing the output
buffer based on the container type resolves the issue.

Fixes: c933bb5 ("telemetry: support array values in data object")

Signed-off-by: Jonathan Erb <jonathan.erb@threater.com>
Acked-by: Ciara Power <ciara.power@intel.com>

.mailmap

@@ -652,7 +652,7 @@ John OLoughlin <john.oloughlin@intel.com>
 John Ousterhout <ouster@cs.stanford.edu>
 John W. Linville <linville@tuxdriver.com>
 Jonas Pfefferle <jpf@zurich.ibm.com> <pepperjo@japf.ch>
-Jonathan Erb <jonathan.erb@banduracyber.com>
+(??)Jonathan Erb <jonathan.erb@threatblockr.com> <jonathan.erb@banduracyber.com>
 Jonathan Tsai <jonathan1.tsai@intel.com>
 Jon DeVree <nuxi@vault24.org>
 Jon Loeliger <jdl@netgate.com>

lib/telemetry/telemetry.c

@@ -160,7 +160,11 @@ container_to_json(const struct rte_tel_data *d, char *out_buf, size_t buf_len)
 		d->type != RTE_TEL_ARRAY_INT && d->type != RTE_TEL_ARRAY_STRING)
 		return snprintf(out_buf, buf_len, "null");
 
-	used = rte_tel_json_empty_array(out_buf, buf_len, 0);
+	if (d->type == RTE_TEL_DICT)
+		used = rte_tel_json_empty_obj(out_buf, buf_len, 0);
+	else
+		used = rte_tel_json_empty_array(out_buf, buf_len, 0);
+
 	if (d->type == RTE_TEL_ARRAY_U64)
 		for (i = 0; i < d->data_len; i++)
 			used = rte_tel_json_add_array_u64(out_buf,