tests/docker: Added docker build support for TSan.

tests/docker: Added docker build support for TSan.

Added a new docker for ubuntu 20.04.
This docker has support for Thread Sanitizer
including one patch we need in one of the header files.
https://github.com/llvm/llvm-project/commit/a72dc86cd

This command will build with tsan enabled:
make docker-test-tsan-ubuntu2004 V=1

Also added the TSAN suppresion file to disable certain
cases of TSAN warnings.

Cc: Fam Zheng <[email protected]>
Cc: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Robert Foley <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Signed-off-by: Alex Bennée <[email protected]>
Message-Id: <20200609200738[email protected]>
Message-Id: <20200612190237[email protected]>