Remove superflous loop in instance queries
Remove superflous loop in instance queries

This patch fixes a piece of convoluted code in the
implementation of instance queries. There was an
unecessarily nested loop, which in case of ongoing
migrations, could throw a key error. This fixes
issue 875.

Signed-off-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>
Reviewed-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>

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