s/Chain(OpQueryExports)/rpc.call_export_list(...)/
s/Chain(OpQueryExports)/rpc.call_export_list(...)/

Parallel opcodes are not (yet?) supported for chaining. Turns out
though that chaining is used only four times in the code, and twice it's
for querying exports. But what's the need to chain the full opcode, when
the simple call_export_list rpc is going to provide the same result?

Reviewed-by: iustinp


mbakke/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,apyrgio/snf-ganeti,mbakke/ganeti,grnet/snf-ganeti,onponomarev/ganeti,andir/ganeti,dimara/ganeti,ganeti/ganeti,yiannist/ganeti,leshchevds/ganeti,ganeti/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,bitemyapp/ganeti,andir/ganeti,leshchevds/ganeti,andir/ganeti,grnet/snf-ganeti,mbakke/ganeti,leshchevds/ganeti,apyrgio/ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,bitemyapp/ganeti,apyrgio/ganeti,yiannist/ganeti,dimara/ganeti