Fix flaky Gitimport integration test

Summary:
The `test-gitimport-with-non-standard-file-mode.t` test was created to test an error condition and how gitimport behaves in such a case. However, since this test was created we added retries to every error in gitimport to provide more resilience to the gitimport process. Owning to those retries, sometimes the expected error message in this test ends up including a retry statement like `retrying attempt 2 of 4...` which ends up making the test flaky.

This diff modifies the test to print only the top 6 lines so we don't even allow the retry line to get included as part of the test output.

Reviewed By: YousefSalama

Differential Revision: D67522222

fbshipit-source-id: f71097061157ce7ddde67fb52f4b18be9dc0c50d

eden/mononoke/tests/integration/gitimport/test-gitimport-with-non-standard-file-mode.t

@@ -52,11 +52,10 @@
   $ git rev-list --objects --all | git cat-file --batch-check='%(objectname) %(objecttype) %(rest)' | sort > $TESTTMP/object_list
 
 # Import it into Mononoke
-  $ with_stripped_logs gitimport "$GIT_REPO_ORIGIN" --derive-hg --generate-bookmarks full-repo
+  $ with_stripped_logs gitimport "$GIT_REPO_ORIGIN" --derive-hg --generate-bookmarks full-repo | head -6
   using repo "repo" repoid RepositoryId(0)
   Execution error: gitimport failed
 
   Caused by:
       0: find_file_changes
       1: Encountered non-standard file mode 0o100744 for file file2 with Object ID f138820097c8ef62a012205db0b1701df516f6d5
-  Error: Execution failed