Bug 963624

+++ This bug was initially created as a clone of Bug #963623 +++

Description of problem:
The libvirt didn't bypass the the file system cache while restoring the guest from managed save file and set the auto_start_bypass_cache = 1 in qemu.conf

Version-Release number of selected component (if applicable):
libvirt-1.0.5-1.el7.x86_64
kernel-3.9.0-0.55.el7.x86_64
qemu-kvm-1.4.0-4.el7.x86_64
How reproducible:
100%

Steps
1.set the auto_start_bypass_cache = 1 in qemu.conf ,then restart libvirtd service
cat /etc/libvirt/qemu.conf
--
auto_start_bypass_cache = 1
--
2. start a guest and make sure the autostart is enabled
#virsh autostart rhelguest1

#virsh start rhelguest1

# virsh dominfo rhelguest1
Id:             1
Name:           rhelguest1
UUID:           fcf773e6-6eba-4e72-8299-de0a38c89136
OS Type:        hvm
State:          running
CPU(s):         1
CPU time:       16.9s
Max memory:     1048576 KiB
Used memory:    1048576 KiB
Persistent:     yes
Autostart:      enable

3.after the guest start completely,managedsave the guest
# virsh managedsave rhelguest1

4 restore the guest directly while the guest managedsave successfully
# virsh start rhel6  
Open another terminal, excute the following command before the guest finished starting,
found that the bypass-cache flag was not included in the following output

#while(true);do cat /proc/$(lsof -w /var/lib/libvirt/qemu/save/rhel6.save|awk '/libvirt_i/{print $2}')/fdinfo/*0*  ;done

this output didn't include the bypass-cache flag

5.however if start the domain with --bypass-cache ,we can get the expect value

# virsh start rhel6  --bypass-cache
Open another terminal, excute the following command before the guest finished starting,
you can see the third value was "4" in flags segment,it means --bypass-cache works

#while(true);do cat /proc/$(lsof -w /var/lib/libvirt/qemu/save/rhel6.save|awk '/libvirt_i/{print $2}')/fdinfo/*0*  ;done
pos:        34603008
flags:        0140000
pos:        163577856
flags:        0140000


Actual results:
In step 4 , we didn't found the bypass-cache flag in the second terminal , so the set about auto_start_bypass_cache=1 in qemu.conf didn't work

Expected results:
As the the auto_start_bypass_cache description in qemu.conf,When a domain is configured to be auto-started, enabling this flag should
has the same effect as using the VIR_DOMAIN_START_BYPASS_CACHE flag with the virDomainCreateWithFlags API.  That is, the system will
avoid using the file system cache when restoring any managed state file however. in my test they are different