* [TD-3197] <fix>: fix taosdemo coverity scan issues.

* [TD-3197] <fix>: fix taosdemo coverity scan issue.

fix subscribeTest pids uninitialized.

* [TD-3197] <fix>: fix taosdemo coverity scan issues.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>