feat: Parser for "ls systemd units"

[jobselko]

All Pull Requests:

Check all that apply:

• Have you followed the guidelines in our Contributing document, including the instructions about commit messages?
• Is this PR to correct an issue?
• Is this PR an enhancement?

Complete Description of Additions/Changes:

This PR aims to consolidate all "ls systemd units" parsers into one file. The combiner will be created afterwards.

MR with relevant changes in insights-core-assets: !437

[xiangce]

@jobselko - Would you like to merge all these ls systems units specs into one? just the ls_etc:

insights-core/insights/specs/default.py

Lines 322 to 325 in bbc2186

	etc_and_sub_dirs = sorted(["/etc", "/etc/pki/tls/private", "/etc/pki/tls/certs",
	"/etc/pki/ovirt-vmconsole", "/etc/nova/migration", "/etc/sysconfig",
	"/etc/cloud/cloud.cfg.d", "/etc/rc.d/init.d"])
	ls_etc = simple_command("/bin/ls -lan {0}".format(' '.join(etc_and_sub_dirs)), keep_rc=True)

e.g.

 systemd_dirs = sorted(["/etc/systemd", "/run/systemd", "/usr/lib/systemd", "/usr/local/lib/systemd"]) 
 ls_systemd_utils = simple_command("/bin/ls -lanRL {0}".format(' '.join(systemd_dirs)), keep_rc=True)

In this way, all the ls results will be wrapped into one simple_file and the combiner you mentioned may be not required.

[psachin]

Hey @jobselko I think we should deprecate the parsers instead of deleting them directly since this is a public repo we don't know whether the parser is already in use /outside Red Hat/. A deprecating warning will alert the user against the alternative parser or the new module where it is migrated (in this case)

[jobselko]

@xiangce I reworked it. Thank you!
@psachin I do not think this is a problem. These parsers are unused (by our teams) and were added around three months ago.

[xiangce]

@jobselko it looks good to me

[jobselko]

I came across these bugs: #3453, #3454

[xiangce]

@jobselko - You missed updating the insights_archive.py file in this PR

[xiangce]

The python26-test in CI failed due to an environmental issue.

Certificate did not match expected hostname: pypi.python.org.

I'll ignore it and merge this PR