pcp-atop: fix upper limit of output pid to 7-digits
pcp-atop: fix upper limit of output pid to 7-digits

pcp-atop displays pid with "%5d".
However, since the pid is 2^22(approximately 4 million) at the maximum,
it is necessary to handle up to 7-digits.

Resolves https://github.com/performancecopilot/pcp/issues/850

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp