Fix LengthInBufferCells test for downlevel
Fix LengthInBufferCells test for downlevel

When running on systems that do not support a virtual terminal,
the tests was incorrectly assuming escape sequences were removed.

The fix is to expect different results depending on whether or not
the host supports virtual terminal mode.

daxian-dbw/PowerShell,PaulHigin/PowerShell,JamesWTruher/PowerShell-1,JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,TravisEz13/PowerShell,PaulHigin/PowerShell,PaulHigin/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1