Fix assert 'treeWithCall == call' (#2050)

Fix assert 'treeWithCall == call' (#2050)

* Fix assert 'treeWithCall == call'

This assert was occurring when we have:
- a potential optimistic tail call
- of a function that returns a ref type
- that is also an inline candidate
- whose inline is rejected
- with `COMPlus_JitGCChecks` stress mode that injects a
call to `CORINFO_HELP_CHECK_OBJ` at the `RETURN`
- where we decide to go ahead with the optimistic tailcall
but it is no longer in legal tailcall position.

To fix, simply disallow a tailcall if we are doing
`COMPlus_JitGCChecks` in a function with a ref type return, that
would have inserted the problemmatic call.

Fixes #1821

* Fix formatting