The when clause that checks if pymysql should be installed from pip
is incorrectly doing an integer comparison against a string value
from the ansible_distribution_major_version variable.
This change resolves that issue by using the version_compare() cast
like was being done for Ubuntu.
Related to: #1665279
Change-Id: Ia3a4bf789cc8e19d7b1f7854cb3ae71c2b8d47e1