Don't use the QRegExp methods that modify the object [QtTest]

Don't use the QRegExp methods that modify the object [QtTest]

QRegExp matching methods modify the object, which we don't want to. In
particular, when we receive a QRegExp from the user or we store in a
context that might require thread-safety, make sure we make a copy
before using it.

QRegularExpression has no such shortcoming.

Task-number: QTBUG-25064
Change-Id: I7c5f5ebf4521c32337c9ea9aeeef50e1e8690bf8
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
Reviewed-by: Jason McDonald <jason.mcdonald@nokia.com>