Merge pull request #351 from yang-g/lsan

Fix a memory leak.

src/core/httpcli/format_request.c

@@ -105,6 +105,8 @@ gpr_slice grpc_httpcli_format_post_request(const grpc_httpcli_request *request,
   }
   gpr_strvec_add(&out, gpr_strdup("\r\n"));
   tmp = gpr_strvec_flatten(&out, &out_len);
+  gpr_strvec_destroy(&out);
+
   if (body_bytes) {
     tmp = gpr_realloc(tmp, out_len + body_size);
     memcpy(tmp + out_len, body_bytes, body_size);