RFR(S): 8238000: Crash in ClassLoader::record_result while dynamic dumping netty

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8238000

webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8238000/webrev.00/

Make a copy of the _shared_path_table for use during dynamic CDS dump. 
It is needed because some Java code continues to execute after dynamic 
dump has finished. However, during dynamic dump, we have modified 
FileMapInfo::_shared_path_table so FileMapInfo::shared_path(i) returns 
incorrect information in ClassLoader::record_result().

Passed tier1 - 4 testing.

thanks,

Calvin