qa/cephfs: replace deprecated assertEquals with assertEqual

qa/cephfs: replace deprecated assertEquals with assertEqual

The unittest.TestCase.assertEquals() method is deprecated in Python 2.7
and emits a DeprecationWarning. This commit replaces all instances of
assertEquals() with the recommended assertEqual() in the cephfs test files
to resolve these warnings and ensure future compatibility.

This change addresses warnings such as:
DeprecationWarning: Please use assertEqual instead.

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>