[TD-4682]<fix>: not move vnode to new dnode within 2 seconds

[TD-4693]add null pointer check

[TD-4642]client subscribe issue

[TD-4701]remove sub query

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

change focal to bionic.

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8 and pip, setuptools

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

install python3.8, and install pip and setuptools

* [TD-4025]<fix>: travis ci broken due to valgrind dependency missed.

modify smoketest.sh to python3.8

* fix timezone build error with clang/linux.

* change fixed version python 3.8 to 3.
Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

hotfix/TD-4675

[TD-i4610]<add special character show>

[TD-4599]<fix>: fix false dnode offline

[TD-4630]<test>: add exception handling for restful insert

[TD-4642]taosd crash for subscribe

[TD-4553]<test>fix timestamp error

sync jdbc driver from develop to master

* cherry pick from develop branch.

* cherry pick from develop branch.

* add static lib link.

[TD-4601]modify error msg

[TD-4620]client crash when insert long string column

* change

* remove test cases not available for master branch
Co-authored-by: NPing Xiao <pxiao@taosdata.com>

END TIME DEALAY 24 HOURS HAS PROBLEMS