[SSSD] [sssd PR#5797][comment] Tests: Install iptabls as its not installed by default

[sgoveas]

URL: https://github.com/SSSD/sssd/pull/5797
Title: #5797: Tests:  Install iptabls as its not installed by default

sgoveas commented:
"""
#5798 covers this requirement. Closing PR.
"""

See the full comment at https://github.com/SSSD/sssd/pull/5797#issuecomment-929089440