Fix `./bin/dev_server pinpoint.yaml`.
Fix `./bin/dev_server pinpoint.yaml`.

The wrapper to run a dev server was effectively constructing a commandline like:

  dev_appserver.py pinpoint.yaml /tmp/deploy-ABCDEF

Which ends up interpreting pinpoint.yaml's handlers in the context of the
current working directory (i.e. the source tree), rather than the carefully
constructed fake-deploy temp directory with all the symlinks in the right
places.

This fix changes the catapult_build/appengine_dev_server.py library to instead
join yaml_paths given to bin/dev_server's commandline to the deploy directory
path, producing a correctly functioning commandline like:

  dev_appserver.py /tmp/deploy-ABCDEF/pinpoint.yaml

This change only affects positional arguments, so flags like --port will still
be passed through as is.

Change-Id: Id1d5db09b4076a8174cdab9fa3c01e2727a0a5a9
Reviewed-on: https://chromium-review.googlesource.com/c/catapult/+/1932860
Reviewed-by: Andrew Bennetts <f07c55753dac44d78e0294a1d64ea321baaa78f4@google.com>
Reviewed-by: Dean Berris <34a37f59e4ade3cf49221306f04217acf3e86255@chromium.org>
Commit-Queue: Andrew Bennetts <f07c55753dac44d78e0294a1d64ea321baaa78f4@google.com>
Commit-Queue: Dean Berris <34a37f59e4ade3cf49221306f04217acf3e86255@chromium.org>
Auto-Submit: Andrew Bennetts <f07c55753dac44d78e0294a1d64ea321baaa78f4@google.com>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult