D7804: tests: avoid grafting the same change over and over

Closed by commit rHGf3ad014b6a53: tests: avoid grafting the same change over and over (authored by martinvonz). This revision was automatically updated to reflect the committed changes. REPOSITORY rHG Mercurial CHANGES SINCE LAST UPDATE https://phab.mercurial-scm.org/D7804?vs=19056&id=19128

D7804: tests: avoid grafting the same change over and over

martinvonz created this revision. Herald added subscribers: mercurial-devel, mjpieters. Herald added a reviewer: hg-reviewers. REVISION SUMMARY The test case added in a1381eea7c7d (graft: do not use `.remove` on a s