ExecuteQuery() is not supported on leveldb state
database.  Currently if called it will panic the peer.
This changeset changes it to a normal error
so that it does not kill the peer process.

Change-Id: Ib9f525524c99b107b4fc3935f2d38a5657bace73
Signed-off-by: denyeart <enyeart@us.ibm.com>