I'm using the f5 software connect to VPN, but errors out with TunnelServer already launched
ps alx | grep svpn | awk '{ print $2 }' | xargs kill -9

Is the generic solution.  Here is the narrative on how I arrived at this solution.
From the BIG-IP f5 application log, you can only find this from the icon in the menu bar.  I saw this line:

2018-06-15, 23:30:54:000, 1274, 1274, edge, 1,    (0xfffffffe)
EXCEPTION - TunnelService, TunnelServer already launched, pid, 1514

I went into my terminal and found this.
ps alx | grep 1514
    0  1514     1   0  31  0  3552740   4212 -      S      ??    0:22.36 /Library/Internet Plug-Ins/F5 SSL VPN Plugin.plugin/Contents/Helpers/svpn svpn
    0  1515  1514   0  31  0  2473600    328 -      S      ??    0:01.54 /Library/Internet Plug-Ins/F5 SSL VPN Plugin.plugin/Contents/Helpers/svpn svpn

Then I issued a kill, but it didn't take.  Luckily a kill -9 worked just fine.
kill -9 1515 1514

So in the future I will be doing a
ps alx | grep svpn | awk '{ print $2 }' | xargs kill -9

This is the generic solution posted at the top.