Cherry-picking the commit from develop since it's also needed for 2.2.
FindASAN did not look for so version 5 and TSAN referred to ASAN. Disable
leak checks for unit tests as some objects always leak, namely servers.
AdressSanitizer is a lightweight memory error detector that instruments at
compile time instead of at execution time. This allows serious memory
errors to be detected without the cost of slowing down the whole program
that often happens when Valgrind is used. It is also easier to enable for
test runs as it is a simple compiler flag.
