feature: add client debug flag

[shaloulcy]

add client debug flag, so we can get more debug info when running
pouch commands

Signed-off-by: Chuanyun Li lcy041536@gmail.com

Ⅰ. Describe what this PR did

Add debug flag in client. So we can get more debug infos when running pouch commands

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how you did it

Add debug flag in client. So we can get more debug infos when running pouch commands

Ⅳ. Describe how to verify it

root@ubuntu-1:~# ./pouch/pouch volume create -D -n volume2  -l like=football -s host=ubuntu1
INFO[0000] start client at debug level                  
DEBU[2018-04-27 11:41:50.937401046] create a volume: volume2, options: [], labels: [like=football], selectors: [host=ubuntu1] 
Labels:       map[backend:local hostname:ubuntu-1 like:football]
Mountpoint:   /mnt/local/volume2
Name:         volume2
Scope:        
Status:       map[sifter:Default]
CreatedAt:    2018-4-27 11:41:50
Driver:       local

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #1234 into master will increase coverage by 0.03%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1234      +/-   ##
==========================================
+ Coverage   15.31%   15.34%   +0.03%     
==========================================
  Files         172      172              
  Lines       10665    10639      -26     
==========================================
  Hits         1633     1633              
+ Misses       8912     8886      -26     
  Partials      120      120

Impacted Files	Coverage Δ
cli/cli.go	0% <0%> (ø)	⬆️
daemon/mgr/network.go	3.47% <0%> (-0.01%)	⬇️
cli/run.go	0% <0%> (ø)	⬆️
cli/update.go	0% <0%> (ø)	⬆️
daemon/mgr/container.go	0% <0%> (ø)	⬆️

[rudyfly]

Our log's TimeStampFormat has been changed to "time.RFC3339Nano" and delete ForceColors, can you change this format like this:

	formatter := &logrus.TextFormatter{
		FullTimestamp:   true,
		TimestampFormat: time.RFC3339Nano,
	}

[rudyfly]

LGTM