Minor issues during MetaspaceShared::initialize_runtime_shared_and_meta_spaces

I noticed this issue while looking into shared space and class space allocations for dynamic archiving. In MetaspaceShared::initialize_runtime_shared_and_meta_spaces(), the compressed class space start is computed as cds_base+cds_total_size. The cd_total_size is MetaspaceShared::core_spaces_size(), which is only valid at dump time. At runtime, MetaspaceShared::core_spaces_size() is 0. As as result, it tries to allocate the class space at the beginning of the mapped shared space, and the first ReservedSpace() fails (in Metaspace::allocate_metaspace_compressed_klass_ptrs). Then it needs to retry at an address that 1G above the initial address.

There is another issue with MetaspaceShared::initialize_runtime_shared_and_meta_spaces(). If shared space mapping fails due to shared_path validation failure, map_shared_spaces() may still return 'true'. That is because FileMapInfo::validate_shared_path_table() does not handle shared_path(i)->validate failure properly. The 'else' case in MetaspaceShared::initialize_runtime_shared_and_meta_spaces would not be taken in that case.