chore(python): add kokoro configs for periodic builds against head (#131

)

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Source-Link: googleapis/synthtool@79c8dd7

packages/google-cloud-python-speech/synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/python-speech.git",
-        "sha": "c211b69003d6adc3ff584431f217251fda057424"
+        "sha": "59745644b08328c883e71d53f3fcc5537644e3c7"
       }
     },
     {
@@ -19,14 +19,14 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "eda422b90c3dde4a872a13e6b78a8f802c40d0db"
+        "sha": "79c8dd7ee768292f933012d3a69a5b4676404cda"
       }
     },
     {
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "eda422b90c3dde4a872a13e6b78a8f802c40d0db"
+        "sha": "79c8dd7ee768292f933012d3a69a5b4676404cda"
       }
     }
   ],
@@ -83,16 +83,21 @@
     ".kokoro/samples/lint/presubmit.cfg",
     ".kokoro/samples/python3.6/common.cfg",
     ".kokoro/samples/python3.6/continuous.cfg",
+    ".kokoro/samples/python3.6/periodic-head.cfg",
     ".kokoro/samples/python3.6/periodic.cfg",
     ".kokoro/samples/python3.6/presubmit.cfg",
     ".kokoro/samples/python3.7/common.cfg",
     ".kokoro/samples/python3.7/continuous.cfg",
+    ".kokoro/samples/python3.7/periodic-head.cfg",
     ".kokoro/samples/python3.7/periodic.cfg",
     ".kokoro/samples/python3.7/presubmit.cfg",
     ".kokoro/samples/python3.8/common.cfg",
     ".kokoro/samples/python3.8/continuous.cfg",
+    ".kokoro/samples/python3.8/periodic-head.cfg",
     ".kokoro/samples/python3.8/periodic.cfg",
     ".kokoro/samples/python3.8/presubmit.cfg",
+    ".kokoro/test-samples-against-head.sh",
+    ".kokoro/test-samples-impl.sh",
     ".kokoro/test-samples.sh",
     ".kokoro/trampoline.sh",
     ".kokoro/trampoline_v2.sh",