virresctrl: fix starting VMs with cputune.memorytune specified

virresctrl: fix starting VMs with cputune.memorytune specified

When removing check for return value of VIR_EXPAND_N this place was
incorrectly modified causing failure to start a VM with cputune
memorytune configured with useless error message:

    error: Failed to start domain 'vm1'
    error: An error occurred, but the cause is unknown

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1973094
Fixes: 7d2fd6ef0163a939adb7ce0f0fad3b7654c340de
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>