RFR(M): 8201375: Add the AllowArchivingWithJavaAgent diagnostic vm option to allow the use of the -javaagent option during CDS dumping

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8201375

webrev: http://cr.openjdk.java.net/~ccheung/8201375/webrev.00/

This change is for adding a diagnostic vm option 
(AllowArchivingWithJavaAgent) to allow the -javaagent in the command 
line during CDS dumping. Please refer to the corresponding CSR 
(https://bugs.openjdk.java.net/browse/JDK-8213813) for details.

Testing: ran hs-tier{1,2,3} tests through mach5.

thanks,
Calvin