Return value other that 0 results in "Unexpected exit status"

Describe the bug

When a guest program exits with any non-zero return value, H2's booter reports FAIL Unexpected exit status. and exits with code 1, instead of cleanly returning the guest's actual return value. A guest that returns 0 still works correctly.

To Reproduce

Steps to reproduce the behavior:

• Create a guest program that returns non-zero:

#include <stdio.h>
int main(){
    printf("\nPRINTF\n");
    return 100;
}

• Compile and run.
• Check the exit code: echo $? — observe it is 1 (with FAIL ... Unexpected exit status. in the output) instead of 100.
  (Any non-zero return value reproduces this; return 0 still exits cleanly.)
  Expected behavior
  The booter should return/propagate the guest's actual exit status (e.g. 100). $? should equal the guest program's return value.

This bug is introduced by : https://github.com/qualcomm/hexagon-hypervisor/pull/65

Start with the H2 booter's handling of a guest program's exit status and reproduce the issue using the C guest program described in the report, which returns 100. Trace why non-zero guest exits become "Unexpected exit status" and status 1; done means the booter exits with the guest's actual non-zero status while return 0 still works.