<rdar://problem/13404009>
<rdar://problem/13404009>

Only get the attach_info's user ID if the supplied user info is invalid.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@177900 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb