nginx: use official PPA by default
nginx: use official PPA by default

Signed-off-by: Matt Andrews <1383225ebefcea25854db624b43fe2d0e61538a0@csiro.au>

AtlasOfLivingAustralia/ala-install,AtlasOfLivingAustralia/ala-install,AtlasOfLivingAustralia/ala-install,AtlasOfLivingAustralia/ala-install,AtlasOfLivingAustralia/ala-install