adb: don't use <error.h>.

This should fix the bloody Mac build, which doesn't have <error.h>. Since
we weren't entirely happy with error(3) anyway, switch to the toybox
style of error_exit and perror_exit, which are slightly briefer and quite
a bit more intention-revealing.

Bug: N/A
Test: builds
Change-Id: Ic8e411906c363af51657da5ce947b25a0b6bb1f3