Steven J. Horowitz Senior Music Writer A few weeks ago, Killer Mike stood poised at the mic on stage at “The Tonight Show With Jimmy Fallon.” He was joined by acclaimed jazz pianist Robert Glasper and R&B singer Eryn Allen Kane for a stripped-down rendition of “Motherless,” a deeply visceral meditation on the grief he faced from losing his mother and grandmother. “Is this a blessing or a curse, or just some other shit?” he choked through tears streaming down his face.