Changes

test: Remove unused variable Failure
Commit 6ccda11a98afd6f4459e9ff1c24de4ad4450de23 removed its use but
forgot to remove it on this line.
Change-Id: I90375ce1e4b8e0b7e140df908323bc269e0baf40

junit result: also write for aborted runs
Even if aborted due to signal, write a JUnit report XML, and make sure
to indicate the runs as erratic.
Change-Id: I7a334ef3463896c543c0fe592d3903c15e67d4c4

refactor logging: drop 'with', simplify
Refactor logging to simplify use: drop the 'with Origin' style
completely, and instead use the python stack to determine which objects
are created by which, and which object to associate a log statement
with.
The new way: we rely on the convention that each class instance has a
local
'self' referencing the object instance. If we need to find an origin as
a new object's parent, or to associate a log message with, we traverse
each stack frame, fetching the first local 'self' object that is a
log.Origin class instance.
We just call log() and it finds an Origin object to log for.
When an exception happens, we first escalate the exception to where ever
it is handled, and only then the log.log_exn() function finds an Origin
object in the traceback's stack frames.
Hence the 'with log.Origin' happens implicitly, no more hassles.
Furthermore, any frame can place additional information in a local
variable called log_ctx. This automatically inserted in the ancestry
associated with a log statement.
Change-Id: I5f9b53150f2bb6fa9d63ce27f0806f0ca6a45e90

log.Origin: ensure to avoid parent loops
Change-Id: I10a2f956beeda38ba1378eace9453eb911aae1a7