RFR: 8213713: Minor issues during MetaspaceShared::initialize_runtime_shared_and_meta_spaces

[Jiangli Zhou]

Please review the following change for fixing some non-fatal issues 
during MetaspaceShared::initialize_runtime_shared_and_meta_spaces process.

webrev: http://cr.openjdk.java.net/~jiangli/8213713/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8213713

Issue 1)
MetaspaceShared::core_spaces_size() is not populated early enough during 
runtime. As a result, the beginning (instead of the end) address of the 
mapped shared spaces is used as the requested address for reserving the 
compressed class space. So the first ReservedSpace() always fails at 
runtime and we retry with a new address that's 1G higher. That adds 
unwanted overhead and also causes a gap between the mapped shared spaces 
and the compressed class space.

Issue 2)
FileMapInfo::validate_shared_path_table returns true even when 
shared_path(i)->validate() fails.

Issue 3)
Dead code in FileMapInfo::validate_shared_path_table. The 'else if 
(!PrintSharedArchiveAndExit)' is never taken and should be removed.

As part of the change, I've also added some more asserts.

Tested with appcds tests locally on linux-x64. Running tier1-tier3.

Thanks,

Jiangli