Fix style errors

/scratch/jenkins/workspace/plugins/google-storage-plugin/src/main/java/com/google/jenkins/plugins/storage/AbstractUpload.java:30: Wrong order for 'java.util.Hashtable' import.
/scratch/jenkins/workspace/plugins/google-storage-plugin/src/main/java/com/google/jenkins/plugins/storage/AbstractUpload.java:413:22: ',' is not followed by whitespace.
/scratch/jenkins/workspace/plugins/google-storage-plugin/src/main/java/com/google/jenkins/plugins/storage/AbstractUpload.java:413:66: ',' is not followed by whitespace.