OHLC tick offset bug

[etpinard]

from @alexcjohnson

noticed this while fixing test failures in my branch:
https://github.com/plotly/plotly.js/blob/master/test/jasmine/tests/finance_test.js#L515
seems like a bug, no? the first and last points should be at 22:48 and 01:12, same as the other traces, right? It looks like each trace calculates its own minimum x spacing (and with one point this trace has none) but traces really need to share that calculation