4508 4538 7210 flowadm man page improvements

Review Request #2524 — Created March 1, 2020 and submitted — Latest diff uploaded

4508, 4538, 7210
This is a fix for a number of errors in the flowadm(1M) man page, including

    4508 flowadm not working as documented, or documentation incorrect
    4538 flowadm man page does not list lport and rport as output fields for show-flow
    7210 flowadm does not have show-usage command described in the manual page

Note that there's a reference to flowstat(1M), which will be provided shortly.

Viewed the revised man page.