Fixes#496
Previously we do not check whether table is foreign or not while creating empty
shards, and set storage type to 't'(Standard table) or 'c'(Columnar table). Now
if the table is foreign table(but not CStore foreign table) we set storage
type to 'f'(Foreign table). If it is CStore foreign table, we set its storage
type to 'c', i.e. columnar table have priority over foreign table.
Please note that 'c' is only used for CStore tables not for other possible
columnar stores at the moment. Possible improvement could be checking for other
columnar stores, though I am not sure if there is a way to check it for all
other columnar stores.
Burak Yücesoy
Onder Kalaci