qga: Invert logic on return value in main()

qga: Invert logic on return value in main()

Current logic on return value ('ret' variable) in main() is error
prone. The variable is initialized to EXIT_SUCCESS and then set
to EXIT_FAILURE on error paths. This makes it very easy to forget
to set the variable to indicate error when adding new error path,
as is demonstrated by handling of initialize_agent() failure.
It's simply lacking setting of the variable.

There's just one case where success should be indicated: when
dumping the config ('-D' cmd line argument).

To resolve this, initialize the variable to failure value and set
it explicitly to success value in that one specific case.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Message-ID: <8a28265f50177a8dc4c10fcf4146e85a7fd748ee.1736261360.git.mprivozn@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>