Code review comment for lp:~julian-edwards/launchpad/missing-slave-method-bug-509383

= Summary =
Add a method to RecordingSlave that was missed during refactoring

== Proposed fix ==
RecordingSlave is missing _sendFileToSlave(). This was missed out during the
refactoring at the Wellington sprint and causes private builds to fail.

== Implementation details ==
The new method just calls RecordingSlave.ensurepresent so the same test for
that is re-used.

== Tests ==
bin/test -vvct TestRecordingSlaves

== Demo and Q/A ==

= Launchpad lint =

Checking for conflicts. and issues in doctests and templates.
Running jslint, xmllint, pyflakes, and pylint.
Using normal rules.

Linting changed files:
  lib/lp/buildmaster/model/builder.py
  lib/lp/buildmaster/tests/test_manager.py
  lib/lp/soyuz/tests/soyuzbuilddhelpers.py
  lib/lp/buildmaster/manager.py
  lib/lp/soyuz/model/binarypackagebuildbehavior.py