Simplify error returns (gosimple)

This fixes:
pkg/api/avatar/avatar.go:261:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/log/file.go:102:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/metrics/graphitebridge/graphite.go:298:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/provisioning/provisioning.go:23:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/alert_notification.go:27:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/alert_notification.go:27:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/annotation.go:105:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/annotation.go:105:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/dashboard.go:351:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/dashboard.go:435:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/dashboard_acl.go:38:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/dashboard_acl.go:38:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/stats.go:22:2: 'if err != nil { return err }; return err' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/team.go:213:2: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:256:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:256:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:274:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:274:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:482:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)
pkg/services/sqlstore/user.go:482:3: 'if err != nil { return err }; return nil' can be simplified to 'return err' (S1013)

pkg/log/file.go

@@ -99,10 +99,7 @@ func (w *FileLogWriter) StartLogger() error {
 		return err
 	}
 	w.mw.SetFd(fd)
-	if err = w.initFd(); err != nil {
-		return err
-	}
-	return nil
+	return w.initFd()
 }
 
 func (w *FileLogWriter) docheck(size int) {