log: fix race
log: fix race

localtime_r() can lead to deadlocks because it calls __tzset() and
__tzconvert() internally. The deadlock stems from an interaction between these
functions and the functions in monitor.c and commands.{c,h}. The latter
functions will write to the log independent of the container thread that is
currently running. Since the monitor fork()ed it seems to duplicate the mutex
states of the time functions mentioned above causing the deadlock.
As a short termm fix, I suggest to simply disable receiving the time when
monitor.c or command.{c,h} functions are called. This should be ok, since the
[lxc monitor] will only emit a few messages and thread-safety is currently more
important than beautiful logs. The rest of the log stays the same as it was
before.

Here is an example output from logs where I printed the pid and tid of the
process that is currently writing to the log:

            lxc 20161125170200.619 INFO     lxc_start:   18695-18695: - start.c:lxc_check_inherited:243 - Closed inherited fd: 23.
            lxc 20161125170200.640 DEBUG    lxc_start:   18677-18677: - start.c:__lxc_start:1334 - Not dropping CAP_SYS_BOOT or watching utmp.
            lxc 20161125170200.640 INFO     lxc_cgroup:  18677-18677: - cgroups/cgroup.c:cgroup_init:68 - cgroup driver cgroupfs-ng initing for lxc-test-concurrent-0

----------> lxc 20150427012246.000 INFO     lxc_monitor: 13017-18622: - monitor.c:lxc_monitor_sock_name:178 - using monitor sock name lxc/ad055575fe28ddd5//var/lib/lxc

            lxc 20161125170200.662 DEBUG    lxc_cgfsng:  18677-18677: - cgroups/cgfsng.c:filter_and_set_cpus:478 - No isolated cpus detected.
            lxc 20161125170200.662 DEBUG    lxc_cgfsng:  18677-18677: - cgroups/cgfsng.c:handle_cpuset_hierarchy:648 - "cgroup.clone_children" was already set to "1".

Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

cjwatson/lxc,ss1h2a3tw/lxc,ysbnim/lxc,thmo/lxc,federicobriata/lxc,hallyn/lxc,federicobriata/lxc,terceiro/lxc,GreatFruitOmsk/lxc,GreatFruitOmsk/lxc,thmo/lxc,caglar10ur/lxc,LynxChaus/lxc,thmo/lxc,ss1h2a3tw/lxc,hallyn/lxc,ysbnim/lxc,LynxChaus/lxc,terceiro/lxc,cjwatson/lxc,ss1h2a3tw/lxc,LynxChaus/lxc,hfuCN/lxc,aeris/lxc,aeris/lxc,hallyn/lxc,GreatFruitOmsk/lxc,caglar10ur/lxc,cjwatson/lxc,terceiro/lxc,hfuCN/lxc,federicobriata/lxc,hfuCN/lxc,ysbnim/lxc,caglar10ur/lxc,aeris/lxc