common/filter: add _filter_bash()

common/filter: add _filter_bash()

This is needed to account for bash 5.1 adding line number annotation
when executing a command via the -c option and it fails.  For example,
"bash -c 'echo foo > /'" will cause bash 5.1 to report:

     bash: line 1: /: Is a directory

instead of:

     bash: /: Is a directory

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>