x86: Incorrect stubs exception handling for flags recovery

Certain instructions need intercepting and emulating by Xen. In some

cases Xen emulates the instruction by replaying it, using an executable

stub. Some instructions may raise an exception, which is supposed to be

handled gracefully. Certain replayed instructions have additional logic

to set up and recover the changes to the arithmetic flags.

For replayed instructions where the flags recovery logic is used, the

metadata for exception handling was incorrect, preventing Xen from

handling the the exception gracefully, treating it as fatal instead.