first() and last() methods do not accept non-null default

[Stan Lagun]

[].first(null) returns null because single optional method parameter means default value
however [].first(123) will result in exception
The same goes for last() method

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/liberty
Review: https://review.openstack.org/278175

[Stan Lagun (slagun)]

Fixed by https://review.openstack.org/278173

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/278173
Committed: https://git.openstack.org/cgit/openstack/yaql/commit/?id=4f72e08888f73981b04f6558ab086fb25fadaa8d
Submitter: Jenkins
Branch: master

commit 4f72e08888f73981b04f6558ab086fb25fadaa8d
Author: Stan Lagun <email address hidden>
Date: Wed Feb 10 04:03:36 2016 +0300

    Wrong parameter default for first()/last() was fixed

    queries module had its own NO_VALUE constant
    that was used for specification of default value for
    first() and last() method arguments.

    Because yaql runtime doesn't know anything about this
    value it assumed that the parameter must be of its default
    value type (type(DEFAULT_VALUE)) or null. Because NO_VALUE
    is not accessible from YAQL expressions the only possible
    default was null value. Or other parameter values caused
    an exception.

    Change-Id: I9518611fa02ec6eb5f43014182750c4c1ddff072
    Closes-Bug: #1543873

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/278175
Committed: https://git.openstack.org/cgit/openstack/yaql/commit/?id=2917427d2950dedcf961f49464abc138e35a4a8f
Submitter: Jenkins
Branch: stable/liberty

commit 2917427d2950dedcf961f49464abc138e35a4a8f
Author: Stan Lagun <email address hidden>
Date: Wed Feb 10 04:03:36 2016 +0300

    Wrong parameter default for first()/last() was fixed

    queries module had its own NO_VALUE constant
    that was used for specification of default value for
    first() and last() method arguments.

    Because yaql runtime doesn't know anything about this
    value it assumed that the parameter must be of its default
    value type (type(DEFAULT_VALUE)) or null. Because NO_VALUE
    is not accessible from YAQL expressions the only possible
    default was null value. Or other parameter values caused
    an exception.

    Change-Id: I9518611fa02ec6eb5f43014182750c4c1ddff072
    Closes-Bug: #1543873