Try to detect ssh and telnet port

[Martin-Zeithaml]

Proposed changes

Try to detect ssh and telnet port by looking into /etc/ssh/sshd_config and /etc/services. If such check fails, set the default port 22 and 23 (same as now).

This PR addresses Issue:

• Auto detect the TN3270 and the ssh ports during the install zowe-install-packaging#292
  • The PR suggested to add this check into configuration process. I believe it is better to do it during the app-server start-up. This approach is independent on the zowe.yaml changes: you can set the Zowe not to use app-server and later change it.
• FSUM7422 node is not found zlux#1022
  • There are 2 confusing messages related to node and as discussed in the issue, this node check is not needed.

Type of change

• New feature (non-breaking change which adds functionality)

PR Checklist

Please delete options that are not relevant.

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have commented my code, particularly in hard-to-understand areas
• Relevant update to CHANGELOG.md
• My changes generate no new warnings

Testing

Small unit test

Test for checking if the logic works as expected:

Input='' -> SSH_PORT=22
Input=' ' -> SSH_PORT=22
Input='123 ' -> SSH_PORT=22
Input='0' -> SSH_PORT=22
Input='asdf' -> SSH_PORT=22
Input='99999' -> SSH_PORT=22
Input='file not found' -> SSH_PORT=22
Input='C:\' -> SSH_PORT=22
Input='1' -> SSH_PORT=1
Input='23' -> SSH_PORT=23
Input='144' -> SSH_PORT=144
Input='65535' -> SSH_PORT=65535

Running without variables

In the log:

ZWED_SSH_PORT=22
ZWED_TN3270_PORT=23

Running with preset ZWED_SSH_PORT

In the log:

ZWED_SSH_PORT=123
ZWED_TN3270_PORT=23

Further comments

I keep the setting in defaults.yaml. It should work without that, because those variables are exported. But in the future, there might be a way how to do it in JavaScript, keep it as reference.