Fix for catchup-only.
Previously when the get_db call succeeded the result of this was not
copied to head.db. This results in incomplete data on this specific
node. I removed this optimization so the node only does regular
catchup.
Merge pull request #430 from Incubaid/fix-catchup-only

Fix for catchup-only.
Merge branch 'incubaid-1.6' into 1.6-for-1.7

Conflicts:
	src/node/catchup.ml
	src/node/node_main.ml