libpod: Fix "top" support on FreeBSD

FreeBSD's ps ignores -J if -a is specified, so "podman top" would
effectively just run ps -a, not terribly useful.  But there's no need to
specify -a when specifying a selector such as -J (or -G or -U, etc.).

Signed-off-by: Mark Johnston <mark.johnston@klarasystems.com>

libpod/container_top_freebsd.go

@@ -57,7 +57,7 @@ func (c *Container) Top(descriptors []string) ([]string, error) {
 		}
 	}
 	if supportedDescriptors {
-		descriptors = []string{"-ao", strings.Join(descriptors, ",")}
+		descriptors = []string{"-o", strings.Join(descriptors, ",")}
 	}
 
 	// Note that the descriptors to ps(1) must be shlexed (see #12452).