cmdlib.py: move _GetQueryImplementation to end of file
cmdlib.py: move _GetQueryImplementation to end of file

_GetQueryImplementation() uses _QUERY_IMPL, which list all query type
implementations. By moving it to the end of the file, we ensure all such
classes are defined by the time we list them.

Signed-off-by: Adeodato Simo <16293852a0900193fe70fa7d24f714f37ba99a56@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

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