Regex patterns were not being escaped properly so package names
containing characters that could be interpreted as regex symbols
were causing failures.
Fixes: #19714
* Fix 'yum skips updates' bug
When the 'yum check-update' output is parsed, the regex used
to stitch wrapped lines together would fail on the first package.
It would fail because there is an empty line before the first
package, and this triggered the regex. To avoid a more complicated
regex, preprocess the check-update output to strip out any
empty lines.
The regex is also updated to include a group on the non whitespace
match to be used in the sub.
Add test cases based on info provided in the bug reports.
Fixes#20608
