SERVER-8795 Lock mongo files in remapPrivateView on Solaris

Prevent other threads from touching the memory of a memory-mapped file
while the file's private view is reset in remapPrivateView() on Solaris.
SERVER-8795 Revert "SERVER-8782 disable smalloplog geo_update_btree.js on Solaris"

This reverts commit cafb1081b84aa443aa0b5c2c12d4d14eaa628a82.

Fixing SERVER-8795 should make geo_update_btree.js not segfault.