Whenever an IO channel is made to a bdev, it gets some pre-allocated
iobufs from SPDK's pre-allocated buffer pools. SPDK has 2 pools, one
with small buffers (8kb per item), and one with large buffers (128kb per
item).
This sizes of these pools are configurable at SPDK startup time.
We were getting crashes in production because of no free items in these
pools.
To fix this, this change:
1. Increases the sizes of these pools.
2. Increases the number of 1g hugepages used for SPDK, to have enough
space for the new sizes of pools
ab3933bc93