[Atlassian] Add support of plaintext to extractJIRA function

Related-To: PRODX-3678
Change-Id: I27ee9ce31e01abc0b7a9bf040e45fb55dd34c592
diff --git a/src/com/mirantis/mk/Atlassian.groovy b/src/com/mirantis/mk/Atlassian.groovy
index 7b06fd1..33abced 100644
--- a/src/com/mirantis/mk/Atlassian.groovy
+++ b/src/com/mirantis/mk/Atlassian.groovy
@@ -48,12 +48,18 @@
 **/
 
 List extractJIRA(String commitMsg, String matcherRegex = '([A-Z]+-[0-9]+)') {
-  String msg = new String(commitMsg.decodeBase64())
-  def matcher = (msg =~ matcherRegex)
-  List tickets = []
+    String msg
+    try {
+        msg = new String(commitMsg.decodeBase64())
+    } catch (e) {
+        // use commitMsg as is if cannot decode so we can use the same function for plaintext too
+        msg = commitMsg
+    }
+    def matcher = (msg =~ matcherRegex)
+    List tickets = []
 
-  matcher.each{ tickets.add(it[0]) }
-  return tickets
+    matcher.each{ tickets.add(it[0]) }
+    return tickets
 }
 
 /**