build: don't instantiate const objects with no user-defined constructor
build: don't instantiate const objects with no user-defined constructor

It seems that some compilers disallow instantiating const objects that
don't provide a user-provided constructor. This would surface as the
following error.

error: default initialization of an object of const type 'const ClusterInfo' requires a user-provided default constructor

Change-Id: Ia21baed51e035d9005453fd7d08274c9c23e74d7
Reviewed-on: http://gerrit.cloudera.org:8080/11971
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <864f6b82bd94e8dda64141d4274519ee66e0102e@cloudera.com>

helifu/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu