Fix cgroup support for recovery mode

In recovery mode a separate set of cgroups should be mounted. Add a
cgroups.recovery.json file to describe cgroups mounted during recovery.
Change cgroups descriptor parset to allow cgroups and cgroups2 sections
to be omitted.

Bug: 124270406
Test: "adb reboot sideload; adb devices" shows 'sideload' as expected

Change-Id: Ic32bd2b4612ec8390064f87d4655d1bd1183d741
Signed-off-by: Suren Baghdasaryan <surenb@google.com>