Set keepalive interval for paramiko SSHClient

If the ssh server has set the option ClientAliveInterval, it will
send an 'empty' packet to a client and closes the connection if
the client is not responding.
Looks like paramiko ignores such keepalive packages from server.

But paramiko has an option similar to ServerAliveInterval, which
allows to send an 'empty' package from the client to the server,
so the server will never reach it's own timeout
for ClientAliveInterval, and the connection won't be closed.

- export SSH_SERVER_ALIVE_INTERVAL=60 # 60 is default, 0 to disable
- remove workarounds for ClientAliveInterval. If the platform set
  this value to 300 for all nodes, the same timeouts may
  happen inside the platform between different components
  and should be catched by the tests in that case.

Change-Id: I552cb7fdca59b51a3fc0e9e7d2cff7f28cb444dc
diff --git a/tcp_tests/templates/shared-salt.yaml b/tcp_tests/templates/shared-salt.yaml
index 330906d..dedc832 100644
--- a/tcp_tests/templates/shared-salt.yaml
+++ b/tcp_tests/templates/shared-salt.yaml
@@ -707,7 +707,7 @@
     -C 'I@salt:master' state.sls openssh &&
     salt --hard-crash --state-output=mixed --state-verbose=False
     -C 'I@salt:master' cmd.run "sed -i 's/PasswordAuthentication no/PasswordAuthentication
-    yes/' /etc/ssh/sshd_config && sed -i 's/ClientAliveInterval 300/ClientAliveInterval 18000/' /etc/ssh/sshd_config && service ssh reload"
+    yes/' /etc/ssh/sshd_config && service ssh reload"
   node_name: {{ HOSTNAME_CFG01 }}
   retry: {count: 3, delay: 5}
   skip_fail: false
@@ -880,7 +880,7 @@
   cmd: salt --hard-crash --state-output=mixed --state-verbose=False -C 'I@linux:system and not cfg01*' state.sls openssh &&
     salt --hard-crash --state-output=mixed --state-verbose=False
     -C 'I@linux:system and not cfg01*' cmd.run "sed -i 's/PasswordAuthentication no/PasswordAuthentication
-    yes/' /etc/ssh/sshd_config && sed -i 's/ClientAliveInterval 300/ClientAliveInterval 18000/' /etc/ssh/sshd_config && service ssh reload"
+    yes/' /etc/ssh/sshd_config && service ssh reload"
   node_name: {{ HOSTNAME_CFG01 }}
   retry: {count: 1, delay: 5}
   skip_fail: false