Fix luxi recvMsg for messages bigger than 4K
Fix luxi recvMsg for messages bigger than 4K

This patch fixes a logic bug in luxi that breaks receive of messages
bigger than 4096 bytes. The send message is not impacted as it uses a
different algorithm.

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