Issue 1548 Fix for has_one association update

[amitsuryavanshi]

Fixes #1548

This pull introduces/changes:

• While creating a association, we are checking if there is any reverse has_one association on target instance, if found we are deleting that association before creating new one. Without this fix the target instance would have two has one relations of same type.

[codecov-io]

Codecov Report

Merging #1549 into master will increase coverage by 0.01%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1549      +/-   ##
==========================================
+ Coverage   93.21%   93.23%   +0.01%     
==========================================
  Files         105      105              
  Lines        4749     4757       +8     
==========================================
+ Hits         4427     4435       +8     
  Misses        322      322

Impacted Files	Coverage Δ
lib/neo4j/active_node/rels.rb	84.61% <100%> (+13.18%)	:arrow_up:
lib/neo4j/active_node/has_n/association.rb	95.51% <100%> (ø)	:arrow_up:
lib/neo4j/active_node/query/query_proxy.rb	94.47% <100%> (+0.06%)	:arrow_up:

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