fix https://github.com/ctripcorp/apollo/issues/2111

[bkblack]

fix #2111.

[codecov-io]

Codecov Report

Merging #2255 into master will decrease coverage by 0.06%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #2255      +/-   ##
============================================
- Coverage        50%   49.93%   -0.07%     
+ Complexity     1982     1980       -2     
============================================
  Files           402      402              
  Lines         12400    12400              
  Branches       1273     1273              
============================================
- Hits           6200     6192       -8     
- Misses         5758     5765       +7     
- Partials        442      443       +1

Impacted Files	Coverage Δ	Complexity Δ
...igservice/controller/NotificationControllerV2.java	86.2% <100%> (ø)	31 <2> (ø)	⬇️
...work/apollo/biz/message/DatabaseMessageSender.java	56.25% <0%> (-10.42%)	6% <0%> (-2%)
...mework/apollo/portal/component/PortalSettings.java	65.07% <0%> (-4.77%)	5% <0%> (ø)

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[coveralls]

Coverage decreased (-0.06%) to 53.508% when pulling 4fe389e on bkblack:master into 989f37b on ctripcorp:master.

[nobodyiam]

LGTM