travis: Reorder builds to speedup testing

Fedora job is slow (12 min vs. ~8 min others), therefore it should be
started earlier (there are 5 jobs running at once, for Fedora we wait
about 3 mins).

Move Centos 6 job up as it's usually the one failing due missing
features (constants etc.) in kernel headers.

Move up openSUSE jobs up, as they're sometimes slow as well.

Reorder Debian oldstable and testing jobs (they were sorted by the OS
release, it's more likely to find a bug in different OS release than
different compiler).

Signed-off-by: Petr Vorel <pvorel@suse.cz>
diff --git a/.travis.yml b/.travis.yml
index 8c3aa24..a295516 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,7 @@
         - os: linux
           env: DISTRO=debian:stable VARIANT=cross-compile.ppc64le TREE="out"
           compiler: powerpc64le-linux-gnu-gcc
+
         - os: linux
           env: DISTRO=debian:stable VARIANT=cross-compile.aarch64 TREE="out"
           compiler: aarch64-linux-gnu-gcc
@@ -23,18 +24,37 @@
           env: DISTRO=debian:stable VARIANT=minimal TREE="out"
           compiler: clang
 
+        # other builds
+        - os: linux
+          env: DISTRO=fedora:latest
+          compiler: clang
+
+        - os: linux
+          env: DISTRO=centos:6 TREE="out"
+          compiler: gcc
+
         - os: linux
           env: DISTRO=debian:testing
           compiler: gcc
+
         - os: linux
-          env: DISTRO=debian:testing
+          env: DISTRO=debian:oldstable
           compiler: clang
 
         - os: linux
+          env: DISTRO=opensuse/tumbleweed
+          compiler: gcc
+
+        - os: linux
+          env: DISTRO=opensuse/leap
+          compiler: gcc
+
+        - os: linux
           env: DISTRO=debian:oldstable
           compiler: gcc
+
         - os: linux
-          env: DISTRO=debian:oldstable
+          env: DISTRO=debian:testing
           compiler: clang
 
         - os: linux
@@ -46,23 +66,8 @@
           compiler: gcc
 
         - os: linux
-          env: DISTRO=opensuse/tumbleweed
-          compiler: gcc
-
-        - os: linux
-          env: DISTRO=opensuse/leap
-          compiler: gcc
-
-        - os: linux
-          env: DISTRO=fedora:latest
-          compiler: clang
-
-        - os: linux
           env: DISTRO=centos:latest
           compiler: gcc
-        - os: linux
-          env: DISTRO=centos:6 TREE="out"
-          compiler: gcc
 
 before_install:
     - DIR="/usr/src/ltp"