db/system_keyspace: Fix "peers" table "schema_version" column type
db/system_keyspace: Fix "peers" table "schema_version" column type

The column type of "schema_version" is set to UTF8 which results in the
following value conversion errors:

  storage_service: fail to update schema_version for 127.0.0.2: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::bad_any_cast> > (boost::bad_any_cast: failed conversion using boost::any_cast)

Change the column type to UUID like in Origin. Fixes #35.

Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@cloudius-systems.com>

linearregression/scylla,kjniemi/scylla,stamhe/scylla,senseb/scylla,respu/scylla,phonkee/scylla,justintung/scylla,rluta/scylla,aruanruan/scylla,duarten/scylla,shaunstanislaus/scylla,justintung/scylla,duarten/scylla,respu/scylla,avikivity/scylla,guiquanz/scylla,rentongzhang/scylla,respu/scylla,capturePointer/scylla,gwicke/scylla,asias/scylla,capturePointer/scylla,wildinto/scylla,acbellini/scylla,scylladb/scylla,stamhe/scylla,rentongzhang/scylla,justintung/scylla,linearregression/scylla,dwdm/scylla,capturePointer/scylla,eklitzke/scylla,victorbriz/scylla,acbellini/scylla,scylladb/scylla,acbellini/scylla,dwdm/scylla,avikivity/scylla,tempbottle/scylla,glommer/scylla,stamhe/scylla,phonkee/scylla,victorbriz/scylla,kangkot/scylla,guiquanz/scylla,raphaelsc/scylla,duarten/scylla,glommer/scylla,senseb/scylla,avikivity/scylla,gwicke/scylla,scylladb/scylla,raphaelsc/scylla,wildinto/scylla,gwicke/scylla,victorbriz/scylla,tempbottle/scylla,eklitzke/scylla,rentongzhang/scylla,raphaelsc/scylla,kjniemi/scylla,wildinto/scylla,eklitzke/scylla,kangkot/scylla,bowlofstew/scylla,phonkee/scylla,dwdm/scylla,aruanruan/scylla,shaunstanislaus/scylla,tempbottle/scylla,senseb/scylla,asias/scylla,bowlofstew/scylla,asias/scylla,glommer/scylla,shaunstanislaus/scylla,rluta/scylla,linearregression/scylla,aruanruan/scylla,guiquanz/scylla,rluta/scylla,kangkot/scylla,kjniemi/scylla,bowlofstew/scylla,scylladb/scylla