travis: Add dummy var to destinguish distro on build status page.

Also enables mysql (for Xenial needs to be explicitly specified)

.travis.yml

@@ -12,22 +12,25 @@ cache:
   directories:
       - $HOME/cachedir
 
+services:
+  - mysql
+
 php:
     - 7.1
 
 matrix:
   include:
     - dist: xenial
-      env: TEST_SUITE="0-*"
+      env: TEST_SUITE="0-*" DIST="xenial"
     - dist: xenial
-      env: TEST_SUITE="1-*"
+      env: TEST_SUITE="1-*" DIST="xenial"
     - dist: xenial
-      env: TEST_SUITE="2-*"
+      env: TEST_SUITE="2-*" DIST="xenial"
 
 env:
-    - TEST_SUITE="0-*"
-    - TEST_SUITE="1-*"
-    - TEST_SUITE="2-*"
+    - TEST_SUITE="0-*" DIST="trusty"
+    - TEST_SUITE="1-*" DIST="trusty"
+    - TEST_SUITE="2-*" DIST="trusty"
 
 install:
   - git clone --depth 1 https://github.com/sstephenson/bats.git $HOME/bats