* Check for available data size in v1/shell.py/_set_data_field, don't
read if 0.
* Add test_shell.py including tests for 3x stdin scenarios:
* closed
* open and empty
* open with data
Change-Id: I6ff65b0e226be509de9cd3f021560081529283b0
Fixes: bug #1173044
Add unittests for the following modules:
* glanceclient.shell
* glanceclient.v1.shell
* glanceclient.v1.legacy_shell
* glanceclient.v2.shell
Also add mock library to the tools/test-requires
Implements: blueprint glanceclient-shells-unittests
Change-Id: I5ec527c5efff3726932d234d7c67e08149643f89