* volume: don't drop the last writable slot on auto-sized disks
MaybeAdjustVolumeMax subtracted 1 from the per-disk slot count, so a disk
with room for exactly one volume (free between 1x and 2x the size limit)
reported 0 slots. The master then never grew a writable volume and every
assign drained its retry budget, so writes failed with context deadline
exceeded. Count the full volumes that actually fit, floored at one for an
auto-sized disk that has free space.
* mini: show disk and volume capacity in the startup banner
Print free space, volume size, total volume count and free volume count
under the data directory line, so a volume size limit that outstrips the
disk is visible at startup instead of surfacing later as failed writes.
Chris Lu
05c6500453