Split certificate API test

Test of certificate API was written as 1 test have 2 function tests.
There is no problem during it runs successfully.
But in case of failure, we cannot find easily about which part of function
was failed. It is not less preferred.
I split the test case as 1 test case checks 1 API.

Change-Id: I679394db42aad1e6e81bf3b023a69827aaf48d70
diff --git a/tempest/api/compute/certificates/test_certificates.py b/tempest/api/compute/certificates/test_certificates.py
index 5299d13..f6cadf7 100644
--- a/tempest/api/compute/certificates/test_certificates.py
+++ b/tempest/api/compute/certificates/test_certificates.py
@@ -20,12 +20,15 @@
 class CertificatesTestJSON(base.BaseV2ComputeTest):
 
     @test.attr(type='gate')
-    def test_create_and_get_root_certificate(self):
+    def test_create_root_certificate(self):
         # create certificates
-        resp, create_body = self.certificates_client.create_certificate()
+        resp, body = self.certificates_client.create_certificate()
         self.assertEqual(200, resp.status)
-        self.assertIn('data', create_body)
-        self.assertIn('private_key', create_body)
+        self.assertIn('data', body)
+        self.assertIn('private_key', body)
+
+    @test.attr(type='gate')
+    def test_get_root_certificate(self):
         # get the root certificate
         resp, body = self.certificates_client.get_certificate('root')
         self.assertEqual(200, resp.status)
diff --git a/tempest/api/compute/v3/certificates/test_certificates.py b/tempest/api/compute/v3/certificates/test_certificates.py
index ce025fc..0ba44cb 100644
--- a/tempest/api/compute/v3/certificates/test_certificates.py
+++ b/tempest/api/compute/v3/certificates/test_certificates.py
@@ -20,12 +20,15 @@
 class CertificatesV3Test(base.BaseV3ComputeTest):
 
     @attr(type='gate')
-    def test_create_and_get_root_certificate(self):
+    def test_create_root_certificate(self):
         # create certificates
-        resp, create_body = self.certificates_client.create_certificate()
+        resp, body = self.certificates_client.create_certificate()
         self.assertEqual(201, resp.status)
-        self.assertIn('data', create_body)
-        self.assertIn('private_key', create_body)
+        self.assertIn('data', body)
+        self.assertIn('private_key', body)
+
+    @attr(type='gate')
+    def test_get_root_certificate(self):
         # get the root certificate
         resp, body = self.certificates_client.get_certificate('root')
         self.assertEqual(200, resp.status)