npm / arborist / #611 / 1

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Rollback when a fatal signal arrives during reification

This also fixes an issue where the rollback did not properly restore the
state if installing a _new_ package, since there was no move required
when creating the sparse tree in that case, resulting in potentially
half-installed deps being left behind.  Found while combing through
testing every rollback for signal handling.

2712 of 2712 branches covered (100.0%)

Branch coverage included in aggregate %.

3757 of 3757 relevant lines covered (100.0%)

540.05 hits per line