Ignore SIGINFO during self-tests.

In the FreeBSD-specific patch, when the environment variable
e2fsprogs_inhibit_SIGINFO exists (whatever its content, even if empty),
do NOT install the SIGINFO handler. Leverage this when running the
self-tests. This is to avoid false negatives during the self-tests due
to interspersed SIGINFO output redirected from stderr to the log files.

Bump PORTREVISION because this changes the e2fsck utility.