common/rc: fix ignoring of errors on

common/rc: fix ignoring of errors on

Commit 0c95c8acb ("common: hide permision warning from mkswap for
exfat") and commit 08e93fa7c ("generic/554: hide permision warning on
exfat") removed a warning by grepping an error out. It however broke
use on older versions of bash such as 4.4.23:

./common/rc: line 2554: syntax error near unexpected token `>'
./common/rc: line 2554: `       MKSWAP_PROG "$fname" 2> >(grep -v 'insecure permission' >&2) >> $seqres.full'

Fix both instances by using a $(foo) to run the executable.

Cc: Pavel Reichl <preichl@redhat.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>