Add test case which verifies the occurrence of #7409.
Make sure there's a line break before writing new key. Fixes #7409.
Remove any trailing white space.
Don't include `kwargs` entries in `args`.
Keep ZMQ version checking simple.
Fix mtime option in file.find

While the docstring indicates that a +/- modifier is accepted for the
mtime argument to file.find, the regex that parses the mtime expression
does not match a leading plus or minus. This commit modifies that regex,
and then uses the +/- modifier to determine whether to match files older
or newer than the difference indicated by the mtime expression.

Fixes #2828.
Fix unit tests regarding `salt.utils.find._parse_interval`
Docstring formatting to style guide.
Adapt test cases to fixed behaviour.
PyZMQ <= 2.1.9 does not have `zmq_version_info`