Fix seed_steps for generator annotation recipes.

scripts/slave/recipes_test/run_presubmit.tools_build.expected

 [
   {
    "cmd": ["[DEPOT_TOOLS_ROOT]/gclient", "config", "--spec", "solutions = [{'url': 'https://chromium.googlesource.com/chromium/tools/build.git', 'managed': True, 'name': 'build', 'deps_file': '.DEPS.git'}]\n"],
    "name": "gclient setup",
    "seed_steps": ["gclient setup", "gclient clean", "gclient sync"]
   },
   {
    "cmd": ["[DEPOT_TOOLS_ROOT]/gclient", "revert", "--nohooks"],
-   "name": "gclient clean"
+   "name": "gclient clean",
+   "seed_steps": []
   },
   {
    "cmd": ["[DEPOT_TOOLS_ROOT]/gclient", "sync", "--nohooks"],
-   "name": "gclient sync"
+   "name": "gclient sync",
+   "seed_steps": []
   },
   {
    "cmd": ["git", "--work-tree", "[SLAVE_BUILD_ROOT]/build", "--git-dir", "[SLAVE_BUILD_ROOT]/build/.git", "config", "user.email", "commit-bot@chromium.org"],
    "name": "git config user.email",
    "seed_steps": ["git config user.email", "git config user.name", "git clean"]
   },
   {
    "cmd": ["git", "--work-tree", "[SLAVE_BUILD_ROOT]/build", "--git-dir", "[SLAVE_BUILD_ROOT]/build/.git", "config", "user.name", "The Commit Bot"],
    "name": "git config user.name"
   },
   {
    "cmd": ["git", "--work-tree", "[SLAVE_BUILD_ROOT]/build", "--git-dir", "[SLAVE_BUILD_ROOT]/build/.git", "clean", "-xfq"],
    "name": "git clean"
   },
   {
    "cmd": ["[DEPOT_TOOLS_ROOT]/apply_issue", "-r", "[SLAVE_BUILD_ROOT]/build/", "-i", 12853011, "-p", 1, "-s", "https://chromiumcodereview.appspot.com", "-e", "commit-bot@chromium.org"],
    "name": "apply_issue"
   },
   {
    "cmd": ["[DEPOT_TOOLS_ROOT]/presubmit_support.py", "--root", "[SLAVE_BUILD_ROOT]/build/", "--commit", "--verbose", "--verbose", "--issue", 12853011, "--patchset", 1, "--skip_canned", "CheckRietveldTryJobExecution", "--skip_canned", "CheckTreeIsOpen", "--skip_canned", "CheckBuildbotPendingBuilds", "--rietveld_url", "https://chromiumcodereview.appspot.com", "--rietveld_email", "", "--rietveld_fetch"],
    "name": "presubmit"
   }
 ]