[CRASH] int 2e with EAX,EDX=0 crashes DynamoRIO on Windows 7 32-bit

**Describe the bug**
DynamoRIO crashes when executing `int 2e` with EAX and EDX previously set to zero. The test is meant to obtain the EIP value of the instruction next to `int 2e`, however the engine crashes with an error in `core\arch\arch.c:3284`.

**To Reproduce**
Attached C source and executable to run the following code:

```
DWORD expectedAddr, foundAddr;
__asm {
xor eax, eax;
xor edx, edx;
int 0x2e;
nextAddr:
mov foundAddr, edx;
mov expectedAddr, offset nextAddr;
}
printf("Expected: %x\tFound: %x\n", expectedAddr, foundAddr);
```

`drrun.exe -- int2e.exe` will crash. Using the `-debug` flag reveals the failed ASSERT statement (see screenshot below).

[int2e.zip](https://github.com/DynamoRIO/dynamorio/files/5710933/int2e.zip)

**Expected behavior**
This test can expose DBI code caches and works only for 32-bit Windows. The trick is to call `int 2e` with a zero syscall ordinal, and Windows will simply expose the address of the instruction next to it in EDX. Upon fixing this crashing error, DynamoRIO should ideally provide the expected `.text` address for the adjacent instruction instead of a code cache one.

**Screenshots**
Using `-debug` for `drrun` exposes the following error at `core\arch\arch.c:3284`:


Triggering an assert statement that checks the syscall method: `new_method == get_syscall_method()`.

**Versions**
I tried the latest DynamoRIO build 8.0.18611-2 on Windows 7 SP1 32-bit.

**Additional context**
Issue #4426 may be related. My guess is that the handling code expects a real syscall to take place here?