[BUG] junos.conn seems to go stale

Description
Sometimes, proxy minions utilizing junos.cli will return without any newlines. This makes the output hard to read.

Setup
Configure and start a junos proxy minion. The bug might be due to long open connections, so wait, if necessary.

Steps to Reproduce the behavior
Execute a cli command.

$ salt <minion-id> junos.cli "show ntp associations no-resolve"
<minion-id>:
    ----------
    message:
        remote refid st t when poll reach delay offset jitter =============================================================================== +xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx x - xx xx xx xx xx xx *xxx.xxx.xxx.xxx  xxx.xxx.xxx.xxx x - xx xx xx xx xx xx
    out:
        True

Expected behavior
Command should output with newlines. Ex:

<minion-id>:
    ----------
    message:

           remote         refid           st t when poll reach   delay   offset  jitter
        ===============================================================================
        +xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      x -  xx xx  xx    xx    xx   xx
        *xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      x -  xx xx  xx    xx    xx   xx
    out:
        True

Versions Report

$ salt --versions-report
Salt Version:
           Salt: 3000.3

Dependency Versions:
           cffi: 1.13.2
       cherrypy: unknown
       dateutil: 2.8.1
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
         Jinja2: 2.10.3
        libgit2: 0.28.2
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: 2.6.1
   pycryptodome: 3.9.7
         pygit2: 1.0.2
         Python: 3.7.5 (default, Oct 17 2019, 12:25:15)
   python-gnupg: 0.4.5
         PyYAML: 5.3.1
          PyZMQ: 19.0.1
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: 4.3.2

System Versions:
           dist:
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-1062.el7.x86_64
         system: Linux
        version: Not Installed

Start by reproducing the junos.cli command against a configured Junos proxy minion, especially after a long-lived connection, and compare the returned message with the expected output. Trace the junos.cli proxy command's handling of the command response; done means the output preserves its newlines and remains readable.