e2scrub_all: make sure fd 3 is closed before running lvm commands

e2scrub_all: make sure fd 3 is closed before running lvm commands

Some versions of cron leave fd 3 open for some unknown reason.  So
when e2scrub_all is run by cron (on non-systemd systems) this results
in an annoying message from the Cron Daemon because lvm will print
warning messages about "leaked file descriptors.  So force close fd 3
at the beginning of e2scrub and e2scrub_all.

Addresses-Debian-Bug: #940240
Signed-off-by: Theodore Ts'o <tytso@mit.edu>