bugzilla - use ssl_ciphersuite to add HSTS

we already use ssl_ciphersuite for the cipher list
but not for the HSTS line even though ssl_ciphersuite
supports adding that as well. so, use it

just like on I4655ebb78b71e for wikitech

Change-Id: I0de0a92f4513ef09abc7d3ed12cfa7be55ec5623
Merge "bugzilla - use ssl_ciphersuite to add HSTS" into production