Add ConfigWriter._UnlockedGetInstanceList/Info()
Add ConfigWriter._UnlockedGetInstanceList/Info()

This patch splits the GetInstanceInfo and GetInstanceList methods into
two parts, one locked one _Unlocked similar to the way nodes are
queried.

Reviewed-by: ultrotter


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