appends a period in front of the instruction file suffix

Author: Anirav Kareddy

src/main/java/software/amazon/encryption/s3/internal/ReEncryptInstructionFileRequest.java

@@ -64,7 +64,7 @@ public Builder newKeyring(RawKeyring newKeyring) {
     }
 
     public Builder instructionFileSuffix(String instructionFileSuffix) {
-      this.instructionFileSuffix = instructionFileSuffix;
+      this.instructionFileSuffix = "." + instructionFileSuffix;
       return this;
     }