Citigroup is scheduled to report first-quarter earnings before the opening bell Tuesday. Here's what Wall Street expects: Citigroup, whose stock is the best performer year-to-date among the large banks, has gotten a boost from its turnaround effort and relatively low valuations. The firm has been streamlining its operations and working through several regulatory consent orders , which it reportedly expects to complete this year. However, with its global footprint, Citigroup is also perceived to