renamed capmanager class functions to its new ones

[not4win]

From pytest version 3.3.0+, the capmanager.suspendcapture and capmanager.resumecapture were renamed to capmanager.suspend_global_capture and capmanager.resume_global_capture, respectively.
The pytest version used here is 4.

[marxwillia]

@not4win please be more descriptive with your PR. Why are these changes necessary? If they address errors, document them. Does this require a change of the tardis_env.yml file?

[not4win]

tardis_env.yml file has pytest version 4.
From pytest version 3.3.0+, the capmanager's suspendcapture and resumecapture functions have been renamed.
Hence they give out error. (Present in test_integration.py file)
These functions have been renamed to capmanager.suspend_global_capture and capmanager.resume_global_capture, respectively.
No change in tardis_env.yml is required. Just renaming them is sufficient.
Reference: https://stackoverflow.com/questions/42760059/how-to-make-pytest-wait-for-manual-user-action (the first solution)

[epassaro]

@not4win is right, method resumecapture was renamed to resume_global_capture in pytest-dev/pytest#2801