Add Server Technology Sentry Switched device fingerprints

[mkienow-r7]

Description

Adds four new Server Technology Sentry Switched device fingerprints, and updates two existing fingerprints. This PR closes #521.

Notes

From Sentry Smart CDU Firmware Revision History:

12-03-30	7.0a	smcdu-v70a.bin	First production release
...
	Changed the FTP server 220 response code (service ready) login banner
		to "220 Sentry Smart CDU <version> FTP server ready.", where
		<version> is currently "v7.0a".

	Changed the web server identification in HTTP response headers to
		"ServerTech-AWS/<version>", where <version> is currently
		"v7.0a".  "AWS" is short for Advanced Web Server.

Motivation and Context

Improved coverage

How Has This Been Tested?

• bundle exec ./bin/recog_verify xml/favicons.xml xml/ftp_banners.xml xml/html_title.xml xml/http_servers.xml xml/http_wwwauth.xml xml/snmp_sysdescr.xml
• rake tests

Types of changes

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

Checklist:

• I have updated the documentation accordingly (or changes are not required).
• I have added tests to cover my changes (or new tests are not required).
• All new and existing tests passed.