Allow CryptographicUsageMask without ENCRYPT/DECRYPT

[csapuntz]

Currently, the client always adds ENCRYPT/DECRYPT to the cryptographic usage mask in a create_symmetric_key operation. For HMAC key types, these operations don't make sense and Fortanix SDKMS refuses the operation.

Add a flag to disable this behavior. Keep the current behavior as default for backward compatibility.

Fixes #455

[codecov-io]

Codecov Report

Merging #456 into master will decrease coverage by <.01%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #456      +/-   ##
==========================================
- Coverage   95.07%   95.06%   -0.01%     
==========================================
  Files          75       75              
  Lines       12672    12674       +2     
==========================================
+ Hits        12048    12049       +1     
- Misses        624      625       +1

Impacted Files	Coverage Δ
kmip/pie/client.py	99.57% <66.66%> (-0.22%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 9fc9c62...8c628e3. Read the comment docs.