If a console doesn't exist, read password from stdin.

When signapk.jar is invoked by scripts like
sign_target_files_apks.py, there is no console as signapk is
invoked using popen(). To support signing of APKs using
software keys with passwords, we need to read
the password from stdin if there is no console.

Change-Id: Icf69ba1e58bf1f91979eaf1d3b91cb202782e8fd
Signed-off-by: adattatr <anisha.dattatraya.kulkarni@intel.com>
Signed-off-by: Brad Geltz <brad.geltz@intel.com>
Ticket: CYNGNOS-1725
(cherry picked from commit 30ca83f1)