ChannelList.query_nds2_availability can't handle 'inf' segment ending

The following snippet should work, but fails because nds2_channel_source returns inf as the segment end time:

from gwpy.detector import ChannelList
ChannelList.query_nds2_availability(['L1:DMT-SNSH_EFFECTIVE_RANGE_MPC.mean,m-trend'], 1131494417, 1131494417+86400*2, host='nds.ligo-la.caltech.edu')

I'm working on a patch to fix and will post a PR.