(port from eight) recover from the SVN operation being interrupted

* in case 'svn info' returns 'E155037' (run 'cleanup' if it was
  interrupted), clobber the checkout

See ticket:3053

Conflicts:
	master/buildbot/steps/source/svn.py
	master/docs/relnotes/index.rst
Merge pull request #1371 from sa2ajj/port-fix-3053

(port from eight) recover from the SVN operation being interrupted
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Merge pull request #1373 from benallard/patch-1

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