tests: Replace time.sleep with eventually

The previous approach was intermittently flake, leading to different
results based on external results.

The check for goroutines numbers now checks for less or equal, as the
goal of the assertion is to confirm no goroutine is being leaked.

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

remote_test.go

@@ -535,10 +535,22 @@ func (s *RemoteSuite) TestPushContext(c *C) {
 	})
 	c.Assert(err, IsNil)
 
-	// let the goroutine from pushHashes finish and check that the number of
-	// goroutines is the same as before
-	time.Sleep(100 * time.Millisecond)
-	c.Assert(runtime.NumGoroutine(), Equals, numGoroutines)
+	eventually(c, func() bool {
+		return runtime.NumGoroutine() <= numGoroutines
+	})
+}
+
+func eventually(c *C, condition func() bool) {
+	select {
+	case <-time.After(5 * time.Second):
+	default:
+		if condition() {
+			break
+		}
+		time.Sleep(100 * time.Millisecond)
+	}
+
+	c.Assert(condition(), Equals, true)
 }
 
 func (s *RemoteSuite) TestPushContextCanceled(c *C) {
@@ -566,10 +578,9 @@ func (s *RemoteSuite) TestPushContextCanceled(c *C) {
 	})
 	c.Assert(err, Equals, context.Canceled)
 
-	// let the goroutine from pushHashes finish and check that the number of
-	// goroutines is the same as before
-	time.Sleep(100 * time.Millisecond)
-	c.Assert(runtime.NumGoroutine(), Equals, numGoroutines)
+	eventually(c, func() bool {
+		return runtime.NumGoroutine() <= numGoroutines
+	})
 }
 
 func (s *RemoteSuite) TestPushTags(c *C) {