I have the same issue with ESXi 5.1 DVD installation on my 3650 M4 (7915) and I tried changing the Boot Mode from 'UEFI and legacy' to 'UEFI' and no luck. Also tried 'Legacy Only' and it still hangs on 'initializing scheduler...' I changed the boot order to legacy only, cdrom, hard-disk0 and still hangs at same point during installation. I tried ESXi 5.5 DVD and it gets past 'initializing scheduler..', but halts with 'cpu panic' error message.
I have two other 3650 M4 (7915) servers that did not have this problem last year....
Anyone have a solution, or workaround?