RFR: 8221478: Disable VerifySharedSpaces by default

[Claes Redestad]

Hi,

VerifySharedSpaces is currently enabled heuristically when running the
JVM with -XX:SharedArchiveFile= - which reduces the startup benefits
of AppCDS for no substantial benefit (no added security; often redundant
integrity checking).

Proposed fix is to leave the flag disabled in all configurations.

Bug:    https://bugs.openjdk.java.net/browse/JDK-8221837
Webrev: http://cr.openjdk.java.net/~redestad/8221478/open.00/

CSR has been filed.

Testing: tier1-4 ongoing

Thanks!

/Claes