I don't find this a problem, it shows that stability and prosperity is growing. Nobody is stopping Somalis from doing these same jobs, except for the stigma against manual labour. We all live/lived in foreign nations, to seek stability and money, so why can't other Africans come to us?
Moreover, those Yemenis have been in Somalia for god knows how long, they're not even Africans, so why should we mind other Africans. It's not like these East African Bantu communities are known for scamming, kidnapping and other crimes. They just want money and peace. Finally, Somalis are the ones who invite and employ them, or it's those foreign NGOs.