Silence cp error when optional ZFS files are unavailable

Users were seeing the following error message printed:

cp: cannot stat ‘/etc/zfs/zdev.conf’: No such file or directory

Both zdev.conf and zpool.cache are optional files. We print a warning
when they are absent, but cp printed its own error in addition to our
warning. We suppress that.

Signed-off-by: Richard Yao <ryao@gentoo.org>

gen_initramfs.sh

@@ -341,7 +341,7 @@ append_zfs(){
 	# Copy files to /etc/zfs
 	for i in /etc/zfs/{zdev.conf,zpool.cache}
 	do
-		cp -a "${i}" "${TEMP}/initramfs-zfs-temp/etc/zfs" \
+		cp -a "${i}" "${TEMP}/initramfs-zfs-temp/etc/zfs" 2> /dev/null \
 			|| print_warning 1 "Could not copy file ${i} for ZFS"
 	done