tests: add test that @commands in debugcommands.py are sorted I felt like inline Python in test-check-code.t was the most appropriate place for this, as other linters in contrib/ seem to be source file agnostic. The test currently fails.

fsmonitor: be robust in the face of bad state fsmonitor could write out bad state if interrupted part way through, and would then crash when it tried to read it back in. Make both sides of the operation more robust - reading state should fail cleanly, and we can use atomictemp to write out cleanly as the file is small. Between the two, we shouldn't crash with an IndexError any more.