EX-1135 lipe: add support to build against centos8

EX-1135 lipe: add support to build against centos8

There's a huge difference between centOS8 and centOS 7 series, especailly
the strict distinction between python2 and python3, and related python
rpms or pypi packages are the same condition.
Following changes are introduced to add support to build against centOS8:
1. the python platform is strict to python2(python2.7)
2. use 'pip2' instead of 'pip' for pypi
3. improve dependency package list (rpm and pypi module), make it can
be acceptable to centOS7.x and centOS8.x
4. fix code sytle issues to make pylint/pep8 on centOS8 happy
5. set encoding via environ "PYTHONIOENCODING" if sys.setdefaultencoding
is gone (python2.7 on centOS8)
6. improve the lipe.spec to support "make rpms" against centOS8

Change-Id: Id172e2a6aa29f382c4d12ff0d2e748e8b0cde444
Signed-off-by: Gu Zheng <gzheng@ddn.com>
Reviewed-on: https://review.whamcloud.com/43483
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Minh Diep <mdiep@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Gaurang Tapase <gtapase@ddn.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>