[Android] Replace print statement with print() function in make_apk.py and extension_manager.py

In Python 3 print statement is forbidden. So, all print statement should
be replaced with print() function.

BUG=XWALK-2544
Merge pull request #2425 from shawngao5/em_print

[Android] Replace print statement with print() function in make_apk.py and extension_manager.py