join_leave_SUITE: fix a compile warning
join_leave_SUITE: fix a compile warning

tectronics/scalaris,tectronics/scalaris,digshock/scalaris,tectronics/scalaris,seyyed/scalaris,digshock/scalaris,tectronics/scalaris,seyyed/scalaris,digshock/scalaris,digshock/scalaris,digshock/scalaris,tectronics/scalaris,tectronics/scalaris,seyyed/scalaris,seyyed/scalaris,seyyed/scalaris,tectronics/scalaris,seyyed/scalaris,digshock/scalaris,digshock/scalaris,seyyed/scalaris