Fix pattern for matching /etc/hosts entries

[drwetter]

grep -w matches also string1-whatsoever so that entries like

192.168.0.10 anystring anystring-apache
192.168.0.11 anystring-tomcat

matched 3 entries over 2 lines.

This PR fixes #2937 by improving the pattern, so that string1 needs a trailing whitespace or a EOL -- besides a leaing whitespace..

What is your pull request about?

• Bug fix
• Improvement
• New feature (adds functionality)
• Breaking change (bug fix, feature or improvement that would cause existing functionality to not work as expected)
• Typo fix
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If it's a code change please check the boxes which are applicable

• For the main program: My edits contain no tabs, indentation is five spaces and any line endings do not contain any blank chars
• I've read CONTRIBUTING.md and Coding_Convention.md
• I have tested this fix or improvement against >=2 hosts and I couldn't spot a problem
• I have tested this new feature against >=2 hosts which show this feature and >=2 host which does not (in order to avoid side effects) . I couldn't spot a problem
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