chore(java): retry staging portion of the release with backoff (#294)

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Synth log will be available here:
https://source.cloud.google.com/results/invocations/4c821a8c-4190-41b5-8c86-6700d407154b/targets

- [ ] To automatically regenerate this PR, check this box.

Source-Link: googleapis/synthtool@68742c6

.kokoro/common.sh

@@ -25,7 +25,6 @@ function retry_with_backoff {
 
     # allow a failures to continue
     set +e
-    echo "${command}"
     ${command}
     exit_code=$?
 

.kokoro/release/stage.sh

@@ -20,19 +20,22 @@ python3 -m pip install gcp-releasetool
 python3 -m releasetool publish-reporter-script > /tmp/publisher-script; source /tmp/publisher-script
 
 source $(dirname "$0")/common.sh
+source $(dirname "$0")/../common.sh
 MAVEN_SETTINGS_FILE=$(realpath $(dirname "$0")/../../)/settings.xml
 pushd $(dirname "$0")/../../
 
 setup_environment_secrets
 create_settings_xml_file "settings.xml"
 
-mvn clean install deploy -B \
-  --settings ${MAVEN_SETTINGS_FILE} \
-  -DskipTests=true \
-  -DperformRelease=true \
-  -Dgpg.executable=gpg \
-  -Dgpg.passphrase=${GPG_PASSPHRASE} \
-  -Dgpg.homedir=${GPG_HOMEDIR}
+# attempt to stage 3 times with exponential backoff (starting with 10 seconds)
+retry_with_backoff 3 10 \
+  mvn clean install deploy -B \
+    --settings ${MAVEN_SETTINGS_FILE} \
+    -DskipTests=true \
+    -DperformRelease=true \
+    -Dgpg.executable=gpg \
+    -Dgpg.passphrase=${GPG_PASSPHRASE} \
+    -Dgpg.homedir=${GPG_HOMEDIR}
 
 if [[ -n "${AUTORELEASE_PR}" ]]
 then

synth.metadata

@@ -4,7 +4,7 @@
       "git": {
         "name": ".",
         "remote": "https://github.com/googleapis/java-scheduler.git",
-        "sha": "246c96200bd5f0d03bf6a1520f75c6edcce078b3"
+        "sha": "da3ae693d781c2e6dd5c63e87f99c9e507bcffcb"
       }
     },
     {
@@ -19,7 +19,7 @@
       "git": {
         "name": "synthtool",
         "remote": "https://github.com/googleapis/synthtool.git",
-        "sha": "7fcc405a579d5d53a726ff3da1b7c8c08f0f2d58"
+        "sha": "68742c6016bf0d16948a572633d17955a8737414"
       }
     }
   ],