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>

3 files changed, 4 insertions, 4 deletions

diff --git a/pkg/domain/filters/containers.go b/pkg/domain/filters/containers.go
index 09ef6201a..1de5aca91 100644
--- a/pkg/domain/filters/containers.go
+++ b/pkg/domain/filters/containers.go
@@ -35,7 +35,7 @@ func GenerateContainerFilterFuncs(filter string, filterValues []string, r *libpo
 					filterValue = ""
 				}
 				for labelKey, labelValue := range labels {
-					if labelKey == filterKey && ("" == filterValue || labelValue == filterValue) {
+					if labelKey == filterKey && (filterValue == "" || labelValue == filterValue) {
 						matched = true
 						break
 					}
diff --git a/pkg/domain/filters/pods.go b/pkg/domain/filters/pods.go
index 685c182ba..ce7028d2a 100644
--- a/pkg/domain/filters/pods.go
+++ b/pkg/domain/filters/pods.go
@@ -124,7 +124,7 @@ func GeneratePodFilterFunc(filter string, filterValues []string) (
 					filterValue = ""
 				}
 				for labelKey, labelValue := range labels {
-					if labelKey == filterKey && ("" == filterValue || labelValue == filterValue) {
+					if labelKey == filterKey && (filterValue == "" || labelValue == filterValue) {
 						matched = true
 						break
 					}
diff --git a/pkg/domain/filters/volumes.go b/pkg/domain/filters/volumes.go
index 69bef4961..7890459f5 100644
--- a/pkg/domain/filters/volumes.go
+++ b/pkg/domain/filters/volumes.go
@@ -39,7 +39,7 @@ func GenerateVolumeFilters(filters url.Values) ([]libpod.VolumeFilter, error) {
 				}
 				vf = append(vf, func(v *libpod.Volume) bool {
 					for labelKey, labelValue := range v.Labels() {
-						if labelKey == filterKey && ("" == filterVal || labelValue == filterVal) {
+						if labelKey == filterKey && (filterVal == "" || labelValue == filterVal) {
 							return true
 						}
 					}
@@ -56,7 +56,7 @@ func GenerateVolumeFilters(filters url.Values) ([]libpod.VolumeFilter, error) {
 				}
 				vf = append(vf, func(v *libpod.Volume) bool {
 					for labelKey, labelValue := range v.Options() {
-						if labelKey == filterKey && ("" == filterVal || labelValue == filterVal) {
+						if labelKey == filterKey && (filterVal == "" || labelValue == filterVal) {
 							return true
 						}
 					}