Conform ODL to TestCasesBase

Conform ODL to TestCasesBase

Now ODLTestCases inherits from TestCasesBase what induces several
modifications of function definitions.
It also renames functest_run to run and run to main and they now
return the code status defined in TestCasesBase instead of True and
False (run_tests.py has been adapted as well).

It checks if errno is equal to EEXIST when makedir raises an OSError
exception.

JIRA: FUNCTEST-353

Change-Id: I88240a9ce8e491dab4c7e6c604f3ecc62cf9edce
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>