[line-buffer] fix resize to use the requested size
[line-buffer] fix resize to use the requested size

When reading in a full message, we need to make sure the buffer
is large enough to accommodate the full thing.

sureshsundriyal/lnav,tstack/lnav,tstack/lnav,tstack/lnav,sureshsundriyal/lnav,tstack/lnav,sureshsundriyal/lnav,sureshsundriyal/lnav