8024176: [macosx] gc/metaspace/ClassMetaspaceSizeInJmapHeap.java failed since jdk8b105, hs25b47

Summary: The code for reading compressed klass pointers in the sa-agent on Mac used readCompOopAddress instead of readCompKlassAddress, this is wrong but has been hidden because compressed oops and compressed klasses has used the same base address in the past.
Reviewed-by: sla, jmasa
Contributed-by: stefan.johansson@oracle.com

agent/src/share/classes/sun/jvm/hotspot/debugger/bsd/BsdAddress.java

@@ -81,7 +81,7 @@ class BsdAddress implements Address {
 
     public Address getCompKlassAddressAt(long offset)
             throws UnalignedAddressException, UnmappedAddressException {
-        return debugger.readCompOopAddress(addr + offset);
+        return debugger.readCompKlassAddress(addr + offset);
     }
 
     //