Unit testing for the rest of blob commands - part 1

[iricigor]

This continues work from #196

We will do it in two steps:

• add simple tests - most of the work done here!
• add complex tests - with mocks and everything (new ticket Unit testing for the rest of blob commands - part 2 #208 )

Simple tests implementation should contain for each of the three classes

• add new private property and constructors to real classes and replace it in the code
• add shared arguments and real arguments tests
• add generic method execute tests, at least with failures

Complex tests should contain this work for all three classes:

• generic method execute with success tests
• real method execute tests

Watch it for FileSystem changes. Some methods are creating new files / directories which should be avoided.

[iricigor]

Starting to add tests for these three commands:

• - ListBlobs
• - GetBlobs
• - SetBlobs

Just for a record, overall code coverage in azmi-main was 39% at the start of this task (255 block covered vs 396 not covered).
Total number of tests was 73 in azmi-main and additional 27 in azmi-commandline

[iricigor]

List of issues that should be solved later:

• add test for absolute-paths in GetBlobs-Tests.cs
• SetBlob test depends on FileSystem commented out

P.S. This list will be updated during work and issues will be created after PR is reviewed.