(PUP-1283) win32-security gem raises a different exception

Previously, puppet relied on win32-security version 0.1.4, which raised
Win32::Security::SID::Error when it failed to resolve a name into a SID.

Newer FFI versions of win32-security raise SystemCallError instead,
which is a StandardError subclass. When trying to run the puppet agent
against newer versions of the library, puppet reports:

Uninitialized constant Win32::Security::SID::Error

This commit changes the rescue to capture SystemCallError instead. This
exception is defined in ruby 1.8.7 and up.