shell_history.js should tolerate extended file ACLs

If jstests/noPassthrough/shell_history.js is running on a system where files can have extended ACL attributes, then the file mode output from GNU ls -l may include a trailing character to indicate the presence of alternate ACLs ('.' (dot) for SELinux or '+' (plus) for other) (reference).

However shell_history.js checks for equality of the whole mode string against "-rw-------", which spuriously breaks in the presence of such a trailing character.