Bootable filter for listening volumes from CLI

Bootable filter for listening volumes from CLI

Currently cinder treats all values passed to it as True
for bootable filter in volume GET call.

For ex, if bootable=invalid, it converts it into True being
bootable as boolean value in db table 'volume'.

Need to update filtering functionality in cinder to address
'True' and 'False' values seperately.

Existing behavior will be kept same.
Only True/False/true/false input handling is done to treat
true/false seperately
(In current behavior, whatever input is passed for boolean
parameter, cinder convetrs it to True)

Implements : blueprint select-volume-through-bootable-option

Closes-Bug: #1535749

Change-Id: I1f1ec20441b28e01bf07bc4f60d848b653e58d58