syntax: Fix some string interpolation errors.

Change-Id: I312fb007da2592e27d81bcc6d99c93a39fb6aa17
diff --git a/vars/functions.groovy b/vars/functions.groovy
index 720b029..ee20762 100644
--- a/vars/functions.groovy
+++ b/vars/functions.groovy
@@ -24,10 +24,10 @@
 
 String getSnapshotFromPublish(publishName, component) {
     def script = """
-        aptly publish show filesystem:public:${release} \
-            | grep -E '^  ${component}[:] .*' \
+        aptly publish show filesystem:public:${publishName} \
+            | grep -E '^  ${component}: .*' \
             | grep 'snapshot'
-            | awk '{ print $2 }'
+            | awk '{ print \$2 }'
     """
 
     return sh(returnStdout: true, script: script).trim()