Adds shutdown hook

[netodevel]

Hi, I had problems running redis-embedded with spring boot in a jenkins pipeline.

Sometimes the redis stop is not efficient leaving the port stuck in the pipeline as a result of which the next job fails.

I added a hook for when the process that started the redis-embedded stops then it forces the redis to stop.

I was unable to create an automated test for this, if anyone has any suggestions I would appreciate it.

when run together with spring it stops the redis in the sequence that spring-context stops.

[codecov-io]

Codecov Report

Merging #11 into master will increase coverage by 0.51%.
The diff coverage is 85.71%.

@@             Coverage Diff              @@
##             master      #11      +/-   ##
============================================
+ Coverage     72.29%   72.81%   +0.51%     
- Complexity      113      116       +3     
============================================
  Files            20       20              
  Lines           509      515       +6     
  Branches         38       38              
============================================
+ Hits            368      375       +7     
  Misses          118      118              
+ Partials         23       22       -1     

Impacted Files	Coverage Δ	Complexity Δ
...ain/java/redis/embedded/AbstractRedisInstance.java	86.95% <85.71%> (+2.82%)	14.00 <2.00> (+3.00)

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[netodevel]

@robertotru, any feedback on this pr?