Fix bug in man build rule

Currently the man page build rule is run without ‘-e’, so the actual
checks in there are just warnings (check-man-warnings,
check-man-dashes).

The patch fixes this and also fixes the man pages which made me see the
problem.

Additionally, check-man-dashes is now verbose, otherwise it's hard to
find out actually where in the page the error is.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>