Added PLASMAGUARD flag to some spacesuits

Added the PLASMAGUARD flag to ERT suits, deathsquad suits, and CE/Atmos suits as requested in 

https://github.com/d3athrow/vgstation13/issues/2369
flages = FPRINT | TABLEPASS | HEADCOVERSEYES | BLOCKHAIR | STOPSPRESSUREDMAGE | PLASMAGUARD