Roll recipe_engine up to the latest

Changelog:
d732be8 [context] Split "env" values and prefixes.
a8816c7 [path] Add "base_path" to __contains__, add get.
e089e51 [url] Update vpython spec protobuf.
264e3ca [step] Remove config indirection.
cfff93a [path] bring PLATFORM back to config.
96221bc [generator_script] Make allowed keys strict and improve error handling.
060325b [path] Cleanup and use "C:\" for test Windows base
6d2596f [generator_script] constrain generator_script to have a stricter API.
c7595ad [file] fix "rmtree" on non-dir path
154ef7e [path] Add concept of a "cleanup" directory.
c916898 [context] fix treatment of None in env.
c40412c [context] Add path prefix/suffix manipulation.
db92090 Update vpython and spec to new text protobuf.
1ec7ad4 [file] add log listings to file.listdir and file.glob_paths.
267b922 [file] Derive user-facing error from StepFailure and set FAILURE status on step.
ddd1990 [bundle] switch implimentation to use git 2.13 attr pathspec.
a64a4d4 [file] No error in remove if file does not exist
e7ce425 [test] only clean up expectations if training was otherwise successful.
09efd6f Remove all mentions of example.py
d878bba [recipe_modules/file] add real file module to engine.

Change-Id: Ib613c69693003676d813440f7f79330df0996a01
diff --git a/infra/config/recipes.cfg b/infra/config/recipes.cfg
index 20253fb..8414b1e 100644
--- a/infra/config/recipes.cfg
+++ b/infra/config/recipes.cfg
@@ -3,7 +3,7 @@
   "deps": {
     "recipe_engine": {
       "branch": "master",
-      "revision": "8ff178b2ec0c099d49ecb1df1c411f487c6bc657",
+      "revision": "d732be8c982f015796f0e620b7b46cff161b137f",
       "url": "https://chromium.googlesource.com/external/github.com/luci/recipes-py.git"
     }
   },