The tag and tag_ext extensions are deprecated for removal, but are not
used widely today [1]. Rather than rehoming these extensions to
neutron-lib and carrying out their deprecation life-cycle for no
apparent reason, this patch proposes we just remove them now.
While [2] initially removed these extensions, we had to revert
them with [3].
Depends-On: I295a5b84eb7fa3439561fa009b7499f94d8df4d2
[1] http://codesearch.openstack.org/?q=from%20neutron.extensions%20import%20(tag_ext%7Ctag)
[2] I0d7bcd789b468b1dd3f7ea13e6751a46203d6778
[3] If16443616eee703b66d57b6422dd451a443fbc64
Change-Id: I97095453610fff114d999a526d67e78119546ff5
87a36cacc6