Add the possibility to choose unit between byte or percent,
and to choose between checking used or free memory.

avoid to return exit code (int) or mem (object)
better return a tuple (mem, error_message) (object, str)

test_check_apachedex_result: also extract promise messages from test methods

test_check_apachedex_result: fix float threshold

remaning -> remaining

free were equal to memory_used
used were equal to memory_free

Allow to hotplug/hotunplug CPU and Memory in VM using qemu QMP client.
Move VNC set password function to qemuqmpclient

/reviewed-on !27

monitor: Add a random delay of maximum 60 seconds to all monitor cron jobs to avoid high load at the first second of every minute.

some jio folders are not needed anymore, webdav is only needed for config folder.
Report results are placed in documents folder so they will not be synced automatically (we can get then when needed)
Use UTC timezone in json result instead of local time.

/reviewed-on nexedi/slapos.toolbox!26

/reviewed-on nexedi/slapos.toolbox!25

/reviewed-on nexedi/slapos.toolbox!24

  Follow up nexedi/erp5@ccbf9007

/reviewed-on !20

/reviewed-on !22

/reviewed-on nexedi/slapos.toolbox!21

use shred path as parameter and print stderr message when shred command fail

/reviewed-on nexedi/slapos.toolbox!18

/reviewed-on nexedi/slapos.toolbox!16

/reviewed-on nexedi/slapos.toolbox!15

/reviewed-on nexedi/slapos.toolbox!14