Fix tink-client gRPC flags for get and delete command

[gianarb]

Description

Playing with the CLI with JWB we noticed that flags related to
tink-client was not properly added to the get and delete command.

This commit fixes the issue.

Why is this needed

I have added the capability to convert gRPC connection options to flags, but they were not attached to the get and delete command in the right way

[codecov]

Codecov Report

Merging #441 (05fc2ce) into master (a69c792) will increase coverage by 0.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #441      +/-   ##
==========================================
+ Coverage   34.82%   35.10%   +0.27%     
==========================================
  Files          47       47              
  Lines        2886     2886              
==========================================
+ Hits         1005     1013       +8     
+ Misses       1789     1781       -8     
  Partials       92       92              

Impacted Files	Coverage Δ
cmd/tink-cli/cmd/delete/delete.go	61.53% <100.00%> (+10.25%)	⬆️
cmd/tink-cli/cmd/get/get.go	67.18% <100.00%> (+6.25%)	⬆️

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