Think of the upcoming concert by the Infamous Stringdusters — who will be joined by up-and-coming bluegrass band Tramped by Turtles — as something of a victory lap. And why not? The Stringdusters’ latest release, “Things That Fly,” certainly merits the attention. That’s saying something for a bluegrass band that has won some of bluegrass’ highest honors for their work, which is often called among the best in roots music. On their latest album, the Stringdusters push the boundaries of their musical style, moving from a rousing version of U2’s classic “In God’s Country,” to the folk anthem “It’ll Be Alright” and into straight bluegrass.