KVM: selftests: x86: Address missing vm_install_exception_handler conversions

Commit b78f4a59

 ("KVM: selftests: Rename vm_handle_exception")
raced with a couple of new x86 tests, missing two vm_handle_exception
to vm_install_exception_handler conversions.

Help the two broken tests to catch up with the new world.

Cc: Andrew Jones <drjones@redhat.com>
CC: Ricardo Koller <ricarkol@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Message-Id: <20210701071928.2971053-1-maz@kernel.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>