Make release() methods safe to use

[codecov[bot]]

Codecov Report

Merging #215 into master will increase coverage by 0.07%. The diff coverage is 89.13%.

@@             Coverage Diff              @@
##             master     #215      +/-   ##
============================================
+ Coverage      73.4%   73.47%   +0.07%     
  Complexity       10       10              
============================================
  Files            87       87              
  Lines          2767     2801      +34     
  Branches        348      355       +7     
============================================
+ Hits           2031     2058      +27     
- Misses          510      515       +5     
- Partials        226      228       +2

Impacted Files	Coverage Δ	Complexity Δ
.../main/java/com/uber/tchannel/messages/Request.java	76.02% <100%> (+2.48%)	0 <0> (ø)	:arrow_down:
...main/java/com/uber/tchannel/frames/ErrorFrame.java	80.95% <66.67%> (-1.55%)	0 <0> (ø)
...main/java/com/uber/tchannel/messages/Response.java	69.42% <80.95%> (+0.85%)	0 <0> (ø)	:arrow_down:
...java/com/uber/tchannel/handlers/RequestRouter.java	72.48% <0%> (-1.83%)	0% <0%> (ø)

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[yoxule]

LGTM