tests/image: remove all distro restrictions

The distro argument and restrictions to run only tests for the same distro
as the host's one were confusing. This commit removes them. Now the behaviour
is following:

By default all the test cases in test case directory are run.
If test cases are given by arguments, they are all run, and test case
directory is ignored.

.travis.yml

@@ -10,13 +10,13 @@ addons:
       - systemd-container
 matrix:
   include:
-    - name: fedora-30
+    - name: f30
       arch: amd64
-    - name: fedora-30
+    - name: f30
       arch: arm64
-    - name: fedora-31
+    - name: f31
       arch: amd64
-    - name: fedora-31
+    - name: f31
       arch: arm64
 
 language: generic
@@ -26,4 +26,4 @@ script:
   # ubuntu's rpm package sets dbpath to ~/.rpmdb, which makes rpm fail...
   - sudo sh -c 'mkdir /etc/rpm; echo "%_dbpath /var/lib/rpm" > /etc/rpm/macros'
   - go test -c -tags travis,integration -o osbuild-image-tests ./cmd/osbuild-image-tests
-  - sudo ./osbuild-image-tests -test.v --distro $TRAVIS_JOB_NAME
+  - sudo ./osbuild-image-tests -test.v test/cases/$TRAVIS_JOB_NAME*

cmd/osbuild-image-tests/main_test.go

@@ -22,11 +22,8 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/osbuild/osbuild-composer/internal/common"
-	"github.com/osbuild/osbuild-composer/internal/distro"
 )
 
-var distroArg = flag.String("distro", "", "which distro tests to run")
-
 type testcaseStruct struct {
 	ComposeRequest struct {
 		Distro   string
@@ -296,7 +293,7 @@ func getAllCases() ([]string, error) {
 }
 
 // runTests opens, parses and runs all the specified testcases
-func runTests(t *testing.T, cases []string, d string) {
+func runTests(t *testing.T, cases []string) {
 	for _, path := range cases {
 		t.Run(path, func(t *testing.T) {
 			f, err := os.Open(path)
@@ -311,19 +308,6 @@ func runTests(t *testing.T, cases []string, d string) {
 				t.Skipf("the required arch is %s, the current arch is %s", testcase.ComposeRequest.Arch, currentArch)
 			}
 
-			if d != "" {
-				if testcase.ComposeRequest.Distro != d {
-					t.Skipf("the required distro is %s, the passed distro is %s", testcase.ComposeRequest.Distro, d)
-				}
-			} else {
-				hostDistroName, err := distro.GetHostDistroName()
-				require.Nil(t, err)
-
-				if testcase.ComposeRequest.Distro != hostDistroName {
-					t.Skipf("the required distro is %s, the host distro is %s", testcase.ComposeRequest.Distro, hostDistroName)
-				}
-			}
-
 			runTestcase(t, testcase)
 		})
 
@@ -339,5 +323,5 @@ func TestImages(t *testing.T) {
 		require.Nil(t, err)
 	}
 
-	runTests(t, cases, *distroArg)
+	runTests(t, cases)
 }