Unity: update Unity REST 5.0.3 and 5.1.0 change

[Murray-LIANG]

Unity 5.0.3 and 5.1.0 removed some deprecated fields of resources. So, storops needs to add new fields to these resources if necessary. Getting old fields will return None instead of raising AttributeError. The client of storops needs to update to use new fields.

1. UnityHostInitiator's source_type is renamed to initiator_source_type.
2. UnityLinkAggregation's parent_storage_processor is renamed to storage_processor.
3. UnityLun's is_compression_enabled is renamed to is_data_reduction_enabled.
4. Use modification_time to check if UnitySnapSchedule is modified or not. is_modified is removed.
5. UnitySystemCapacity's compression_size_saved/ compression_percent/compression_ratio is renamed to data_reduction_size_saved/data_reduction_percent/ data_reduction_ratio.
6. No function/method argument needs to change.

[codecov[bot]]

Codecov Report

Merging #320 into master will increase coverage by 0.08%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #320      +/-   ##
==========================================
+ Coverage   91.60%   91.68%   +0.08%     
==========================================
  Files          99       99              
  Lines       13754    13768      +14     
  Branches     1663     1663              
==========================================
+ Hits        12599    12623      +24     
+ Misses        739      733       -6     
+ Partials      416      412       -4     

Impacted Files	Coverage Δ
storops/unity/enums.py	98.82% <100.00%> (+0.01%)	:arrow_up:
storops/vnx/heart_beat.py	94.44% <0.00%> (+0.46%)	:arrow_up:
storops/lib/version.py	95.97% <0.00%> (+1.34%)	:arrow_up:
storops/unity/parser.py	92.38% <0.00%> (+1.90%)	:arrow_up:
storops/unity/resource/__init__.py	90.25% <0.00%> (+2.11%)	:arrow_up:

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[Murray-LIANG]

Travis CI met some internal errors. Will check it.