trace2: trim whitespace in region messages in perf target format

Avoid unecessary trailing whitespace in "region_enter" and "region_leave"
messages in perf target format.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

trace2/tr2_tgt_perf.c

@@ -452,8 +452,11 @@ static void fn_region_enter_printf_va_fl(const char *file, int line,
 	struct strbuf buf_payload = STRBUF_INIT;
 
 	if (label)
-		strbuf_addf(&buf_payload, "label:%s ", label);
-	maybe_append_string_va(&buf_payload, fmt, ap);
+		strbuf_addf(&buf_payload, "label:%s", label);
+	if (fmt && *fmt) {
+		strbuf_addch(&buf_payload, ' ');
+		maybe_append_string_va(&buf_payload, fmt, ap);
+	}
 
 	perf_io_write_fl(file, line, event_name, repo, &us_elapsed_absolute,
 			 NULL, category, &buf_payload);
@@ -469,8 +472,11 @@ static void fn_region_leave_printf_va_fl(
 	struct strbuf buf_payload = STRBUF_INIT;
 
 	if (label)
-		strbuf_addf(&buf_payload, "label:%s ", label);
-	maybe_append_string_va(&buf_payload, fmt, ap);
+		strbuf_addf(&buf_payload, "label:%s", label);
+	if (fmt && *fmt) {
+		strbuf_addch(&buf_payload, ' ' );
+		maybe_append_string_va(&buf_payload, fmt, ap);
+	}
 
 	perf_io_write_fl(file, line, event_name, repo, &us_elapsed_absolute,
 			 &us_elapsed_region, category, &buf_payload);