ver_linux: net-tools, look for numerical input, not field number

Rely on regex to find the version number, rather than rely on numerical input to be found in a particular input field.
Proposed implementation also eliminates the necessity to invoke 'grep' + 'awk'.

Signed-off-by: Alexander Kapshuk <alexander.kapshuk@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>