Factor out lv info gathering function
Factor out lv info gathering function

The buildJsonReport function will soon have to perform the coupling of
instance data with LVInfo data. In preparation for that, in order to make
it more readable, the instructions for obtaining LVInfos are factored out
in a separate function.

Signed-off-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>
Reviewed-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>

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