Unnecessary logs when starting/ending storage tasks

[nirs]

When starting and ending tasks, we log unhelpful logs:

2022-05-23 12:29:03,998+0300 INFO  (tasks/9) [storage.threadpool.workerthread] START task 539688e9-a899-4d15-9a30-acd0563e5bf0 (cmd=<bound method Task.commit of <vdsm.storage.task.Task object at 0x7f2cb064c7f0>>, args=None) (threadPool:146)

2022-05-23 12:29:04,069+0300 INFO  (tasks/9) [storage.volume] Request to reduce LV cd981010-ac48-49e1-b28b-cbde06c085bf of image 4b72aba2-0668-463d-b856-7f0f7406b6a2 in VG bafd0f16-9aba-4f9f-ba90-46d3b8a29157 with size = 134217728 allowActive = True (blockVolume:692)

2022-05-23 12:29:04,069+0300 INFO  (tasks/9) [storage.lvm] Reducing LV bafd0f16-9aba-4f9f-ba90-46d3b8a29157/cd981010-ac48-49e1-b28b-cbde06c085bf to 128 megabytes (force=True) (lvm:1704)

2022-05-23 12:29:04,160+0300 WARN  (tasks/9) [storage.lvm] Command ['/usr/sbin/lvm', 'lvreduce', '--devices', '/dev/mapper/0QEMU_QEMU_HARDDISK_data-fc-01,/dev/mapper/0QEMU_QEMU_HARDDISK_data-fc-02,/dev/mapper/0QEMU_QEMU_HARDDISK_data-fc-03', '--config', 'devices {  preferred_names=["^/dev/mapper/"]  ignore_suspended_devices=1  write_cache_state=0  disable_after_error_count=3    hints="none"  obtain_device_list_from_udev=0 } global {  prioritise_write_locks=1  wait_for_locks=1  use_lvmpolld=1 } backup {  retain_min=50  retain_days=0 }', '--autobackup', 'n', '--force', '--size', '128m', 'bafd0f16-9aba-4f9f-ba90-46d3b8a29157/cd981010-ac48-49e1-b28b-cbde06c085bf'] succeeded with warnings: ['  WARNING: Reducing active and open logical volume to 128.00 MiB.', '  THIS MAY DESTROY YOUR DATA (filesystem etc.)'] (lvm:358)

2022-05-23 12:29:04,192+0300 INFO  (tasks/9) [storage.threadpool.workerthread] FINISH task 539688e9-a899-4d15-9a30-acd0563e5bf0 (threadPool:148)

In this case the actual operation was logged by the task:

2022-05-23 12:29:04,069+0300 INFO  (tasks/9) [storage.volume] Request to reduce LV ...

And in lvm:

2022-05-23 12:29:04,069+0300 INFO  (tasks/9) [storage.lvm] Reducing LV ...

The task START/FINISH logs do not add interesting info, except the task id, which
is the only way to locate a task after a task is started by the API.

Fix:

• Include the task id in all task logs, so we can follow all task logs using the task id and we don't need the start/finish logs.
• Change the START/FINISH logs to DEBUG level