sending stderr output from cat command to /dev/null

Description
I took a look at this 'old' issue and the problem is easier than it seems.

Look at this example:

    kz@krasno:manual> export pidFile=/tmp/123
    kz@krasno:manual> kill $(cat $pidFile) 2> /dev/null
    cat: /tmp/123: No such file or directory
    kz@krasno:manual> kill $(cat $pidFile 2> /dev/null) 2> /dev/null

The second redirection to /dev/null isn't for what's inside the parenthesis.
We needed another redirection inside the parenthesis, that's all

This PR solved the bug Issue #400