net-mgmt/py-ncclient: Update to 0.6.4

While I'm here:

• Pet portlint

Changelog:

• Pin selectors2 to Python versions <= 3.4 (and remove the now obsolete patch-requirements.txt)
• Fix config examples to actually use the nc namespace
• Fix: Correctly set port for paramiko when using ssh_config file
• Test: Add test to check ProxyCommand uses correct port
• Update commits for py3
• Enhance Alcatel-Lucent -support
• Juniper RPC: Allow specifying format in CompareConfiguration
• Parsing of NETCONF 1.1 frames no longer decodes each chunk of bytes...
• Fix filter in create_subscription
• Validate 'with-defaults' mode based on supported modes advertised in capability URI

PR: 237154
Submitted by: Sergey Akhmatov (maintainer)
Approved by: mentors (implicit)