[WSL] Expression return value incorrectly in watch window

Internal bug id:394231
Configuration:
OS: Build 15150.rs_onecore_base_bpt1.170305-1700
VSCode: 1.10.2

Repro Steps:

1. Download attachment and copy it to Bash side. app2.zip
2. Open attachment in VSCode and use "C++(GDB/LLDB)" Configuration,update "program" "pipeTransport" "cwd" and "sourceFileMap"Configuration in lanuch.json file as following:
   "program": "/home/grace/temp/app2/a.out",
   "cwd": "/home/grace/temp/app2",
   "pipeTransport": {
   "pipeCwd": "${workspaceRoot}",
   "pipeProgram": "c:\windows\sysnative\bash.exe",
   "pipeArgs": ["-c"],
   "debuggerPath": "/usr/bin/gdb"
   },
   "sourceFileMap": {
   "/home/grace/temp/app2": "c:\temp\app2"
   },
3. Set a breakpoint at the line which contains text "int c=a/b;"
4. Press F5 to start debugging
5. Add expresion 'a/b' in watch window

Expected:
Return a message as "Divide By Zero"

Actual:
As following the pic: