updated shoal-agent spec file to work with the latest code

[MCatherine1994]

• added steps for add/ user/group shoal, but this will raise an error if user/group already exists, wondering if we could check if before adding them
• removed steps related to the previous shoal-agent.sysconfig file
• includes the new shoal-agent-installation fil, otherwise will raise the unpacked file error
• change the onwer of shoal_agent.log file to shoal
• install python module pystun through pip command, as didn't find one could be installed through yum
• create another spec file for python3

[MarcusEbert]

We can check /etc/group (for group) and /etc/passwd (for user) for existing entries before creating the group or user. e.g. for group check something like this should work: if [ $(grep -c "^shoal" /etc/group) -eq 0 ]; then groupadd shoal fi