poky.conf: Update the distros we test against on the autobuilder

(From meta-yocto rev: e2bad29f075d668d70b55f85aec4fd6039e7c119)

(From meta-yocto rev: 7c7856b863f43dc1d88e7ce343e52336cf7bf4fd)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-poky/conf/distro/poky.conf

@@ -67,14 +67,12 @@ SANITY_TESTED_DISTROS ?= " \
             poky-2.5 \n \
             poky-2.6 \n \
             ubuntu-16.04 \n \
-            ubuntu-16.10 \n \
-            ubuntu-17.04 \n \
-            fedora-26 \n \
+            ubuntu-18.04 \n \
+            fedora-28 \n \
             centos-7 \n \
             debian-8 \n \
             debian-9 \n \
-            opensuse-42.1 \n \
-            opensuse-42.2 \n \
+            opensuse-42.3 \n \
             "
 #
 # OELAYOUT_ABI allows us to notify users when the format of TMPDIR changes in