mcpu: Start locking at correct level
mcpu: Start locking at correct level

Commit 8716b1d added a new lock level, LEVEL_NODE_ALLOC. It is ahead of
LEVEL_INSTANCE. The latter was hardcoded in mcpu to be locked right
after the BGL, effectively ignoring LEVEL_NODE_ALLOC.

Signed-off-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

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