daily_ringmap fails if kotekan-ringmap is still in the process of filling frequencies

[anjakefala]

kotekan-ringmap doesn't provide a fixed-length array until it has filled in all of the frequencies. This will be particularly relevant close to restarts.

The analyzer assumes a fixed-length array:

May 15 03:00:16 marimba dias[27687]: ValueError: operands could not be broadcast together with shapes (4982,) (4981,)
May 15 03:00:16 marimba dias[27687]:     t_offset = time["ctime"] - common_time["ctime"]

The analyzer should chop off the difference and still produce a comparable output after restarts.

Relevant to: #153