Searching repositories with `src action exec` fails if they're being cloned

[mrnugget]

When repositories are cloning and I run src action exec with a scopeQuery that includes repositories that are being cloned, the whole search fails:

go install ./cmd/src && src -v actions exec -cache ~/tmp -timeout 5m -f ~/work/src-actions/alpine-sed-replace.action.json | src campaign plan create-from-patches
Querying http://localhost:3080 for repositories matching 'repo:sourcegraph'...
GraphQL errors:
[
  {
    "message": "repository does not exist: github.com/sourcegraph/create-extension",
    "path": [
      "search",
      "results",
      "results",
      20,
      "defaultBranch"
    ]
  },
  {
    "message": "repository does not exist: github.com/sourcegraph/babel-plugin-transform-react-hot-loader-wrapper",
    "path": [
      "search",
      "results",
      "results",
      11,
      "defaultBranch"
    ]
  },