Use PyCrypto to generate randomness passwords

Standard random generator is not secure enouph. Use PyCrypto instead.
Updated requirements.txt with pycrypto>=2.6 according to
global-requirements

Change-Id: I38fd47a30893a946de30fad95c57759781312be6
Closes: bug #1319639
Merge "Use PyCrypto to generate randomness passwords"