Now that we have a CP2 exception CHERI_EXCCODE_TLBSTORE, teach 'cheritest
cheritest_vm_notag_tmpfile_shared' to expect it.
Invert an incorrect test setting (or not setting) TLB limitations on
capability use for VM objects: we want to allow capability use for
default and anonymous objects, and disallow it for other object types
(e.g., vnode-backed memory mappings without copy-on-write).

Simple VM tests for disallowing tags now pass, but there is more work
to do as some of the paths to pmap_enter()-like calls don't accept
PMAP_ flags (currently).