chg: [doc] Added more changes to the RHEL/CentOS install doc.
chg: [doc] Added more changes to the RHEL/CentOS install doc.

SteveClement/MISP,FIRSTdotorg/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,FIRSTdotorg/MISP,SteveClement/MISP,MISP/MISP,MISP/MISP,MISP/MISP,FIRSTdotorg/MISP,FIRSTdotorg/MISP,SteveClement/MISP,MISP/MISP