The ornamental design for a drum lug, as shown and described.
1. Drum lug
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
The dashed broken lines illustrate portions of the drum lug and form no part of the claimed design; the dot-dashed lines in figs. 1.1 to 1.6 define boundaries of the claimed design and form no part thereof.