Update openconfig-mpls-te.yang

[mryuezhang]

Fixes #889

Change Scope

• Added a leaf to MPLS P2P tunnels to enable/disable record-route
• This change is backwards compatible

Platform Implementation

• Cisco IOS XR disables RRO by default.
• JunOS enables RRO by default.

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[OpenConfigBot]

Major YANG version changes in commit 16ac139:

[OpenConfigBot]

Compatibility Report for commit 16ac139:
✅ pyangbind@6b85c2b

[dplore]

Please update leaf names

[dplore]

Thanks @mryuezhang ! As a last step, OpenConfig requires providing references to the documentation for at least two implementations of this change. An example is #941

[jhaas-pfrc]

Note that Junos has RRO on by default.
Since this leaf does not specify a default, it doesn't interfere with existing operations. It provides access to the state of this feature, and provides the ability to disable it explicitly - if desired.

https://www.juniper.net/documentation/us/en/software/junos/mpls/topics/ref/statement/record-edit-protocols-mpls.html

[mryuezhang]

Thanks @mryuezhang ! As a last step, OpenConfig requires providing references to the documentation for at least two implementations of this change. An example is #941

Added.

[dplore]

Please update the version numbers and then we will be ready to merge.