D55859 has no effect for some of the testcases so this patch extends it even for (all?) other testcases known to me. LLDB was failing when LLDB prints errors reading system debug infos (*-debuginfo.rpm, DWZ-optimized) which should never happen as LLDB testcases should not be affected by system debug infos.
lldb/packages/Python/lldbsuite/test/api/multithreaded/driver.cpp.template is using only SB API which does not expose ModuleList so I had to call HandleCommand() there.
lldb-test.cpp could also use HandleCommand and then there would be no need for ModuleListProperties::SetEnableExternalLookup() but I think it is cleaner with API and not on based on text commands.