Use immutable default values for args

Default mutable values (e.g. arg1=[], arg2={}) could have side effects
in Python. So using None as a default value is safer.

Added hacking checks for default mutable args.

Closes: bug #1327473

Change-Id: I7055e534b91df794550de6c3b243324e582d4430
Add explicit import of _ to hp_3par_fc and iscsi

Messages using translation were added to the hp_3par_fc and
hp_3par_iscsi files but an explicit import of gettextutils _ was not
included.

This fixes that problem.

Change-Id: I2555860c6525a00295e823ab8c826b2bec6a3098
Closes-Bug: 1347184
Merge "Use immutable default values for args"
Merge "Add explicit import of _ to hp_3par_fc and iscsi"