Fix printing in rosbag

To see bug that first commit fixes call 'rosbag compress' on any bagfile that updates the progress bar multiple times.  Also look at the output of 'rosbag --help' (that's what changing print -> print() fixes).

To an example of the bug that the second commit fixes, run <tt>rosbag info foo foo</tt>   There should be two error messages on the same line before the commit.  The commit should change it so that the errors are on separate lines.

These all look like bugs introduced when changing from the print statement to the print function.