Recipes: remove some pragma: no cover

These are the remaining instances, and they're harder to deal with:
$ git grep pragma
recipe_modules/swarming/api.py:    except self.m.step.StepFailure as e:  # pragma: no cover
recipe_modules/swarming/api.py:      if len(ids) > 1:  # pragma: nocover
recipes/ct_skps.py:  if api.path.exists(version_file):  # pragma: nocover
recipes/ct_skps.py:  if api.path.exists(blacklist_file):  # pragma: nocover
recipes/upload_nano_results.py:  if len(results) != 1:  # pragma: nocover

Bug: skia:6473
Change-Id: If75e2ffcf39a944b513b9005bbc4bd9c4fb031f6
Reviewed-on: https://skia-review.googlesource.com/13867
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
80 files changed