os/GenericObjectMap.cc: pass big parameter by reference

CID 1188142 (#1 of 1): Big parameter passed by value (PASS_BY_VALUE)
 pass_by_value: Passing parameter header of type
 GenericObjectMap::_Header (size 176 bytes) by value.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>