Fix problems reported by staticcheck

`staticcheck` is a golang code analysis tool. https://staticcheck.io/

This commit fixes a lot of problems found in our code. Common problems are:
- unnecessary use of fmt.Sprintf
- duplicated imports with different names
- unnecessary check that a key exists before a delete call

There are still a lot of reported problems in the test files but I have
not looked at those.

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/libpod/image/prune.go b/libpod/image/prune.go
index 3c06a89c2..587c99333 100644
--- a/libpod/image/prune.go
+++ b/libpod/image/prune.go
@@ -29,7 +29,7 @@ func generatePruneFilterFuncs(filter, filterValue string) (ImageFilter, error) {
 				return false
 			}
 			for labelKey, labelValue := range labels {
-				if labelKey == filterKey && ("" == filterValue || labelValue == filterValue) {
+				if labelKey == filterKey && (filterValue == "" || labelValue == filterValue) {
 					return true
 				}
 			}