Fixed RCG target mode modification issue

[ansarars]

remote copy group target mode change was throwing error.
After analysis it is found that ansible code was not converting sync/periodic/async with their enum values 1/3/4 hence modification was failing.
Note: wsapi accepts enum values of target mode hence it failed.

[sneharai4]

Changes looks good to me. Please add unit tests for this.

[ansarars]

Unit test case run results:-
root@CSSOSBE03-B05:/home/Arshad/workspace/modify_rcg_issue/hpe3par_ansible_module# python -m pytest test/unit/test_hpe3par_remote_copy.py
============================================================================== test session starts ==============================================================================
platform linux2 -- Python 2.7.12, pytest-4.3.0, py-1.8.0, pluggy-0.9.0
rootdir: /home/Arshad/workspace/modify_rcg_issue/hpe3par_ansible_module, inifile:
plugins: requests-mock-1.5.2
collected 28 items

test/unit/test_hpe3par_remote_copy.py ............................ [100%]

=============================================================================== warnings summary ================================================================================
/usr/local/lib/python2.7/dist-packages/dns/hash.py:25
/usr/local/lib/python2.7/dist-packages/dns/hash.py:25: DeprecationWarning: dns.hash module will be removed in future versions. Please use hashlib instead.
DeprecationWarning)

-- Docs: https://docs.pytest.org/en/latest/warnings.html
===================================================================== 28 passed, 1 warnings in 4.39 seconds =====================================================================
root@CSSOSBE03-B05:/home/Arshad/workspace/modify_rcg_issue/hpe3par_ansible_module#

[sneharai4]

@ansarars Please close this PR if not needed.