By Michelle Nichols UNITED NATIONS (Reuters) -Malian government troops and “white-skinned soldiers” detained 33 civilians in central Mali in March who were later found shot dead and their bodies burned, sanctions monitors told the U.N. Security Security Council in a report seen by Reuters on Friday. The report does not identify the “white-skinned soldiers” who are accused of rounding up men and older boys in a small Malian village, tying their hands behind their backs and blindfolding them. Malian troops then arrived and are accused of beating the men and taking away 29 Mauritanians and four M…