exit1(): Reword comment regarding init workaround

There are other relatively common reasons why init might get killed
during reboot, the workaround was really not sparc64-specific.

(cherry picked from commit 96c76d930656f13d3c041dc8d8f2fc3dd1e5e05a)
(cherry picked from commit 28b36ecf990fc28a935ab2ce75f7504721c3a7ea)