Do a little more logging of flushes and snapshots
Add the rest of the NDS server params to the info nds output
Clear dirty_keys in flushDirtyKeys

Defrag requires that there are no dirty keys, so let's make that clear.  This also
means that anything that runs flushDirtyKeys in the foreground doesn't have to clear
the dirty list itself, so I ripped that couple of lines out of redis.c.
Log whenever an NDS command is requested
Rework the defrag/snapshot logic a bit to iron out some bugs
Turn down a whole pile of logs to DEBUG
Fix potential crash when reporting failure of an NDS DEFRAG/SNAPSHOT