Improve timeout for GNMI dbus service (sonic-net#265)

Why I did it
Currently we are using 60 seconds as timeout for GNMI dbus API, if GCU takes several minutes, GNMI will fail.
Microsoft ADO: 27231413

How I did it
Now we use 180 seconds as timeout, and this is the same as NDM timeout for GCU.

How to verify it
Run GNMI unit test and end to end test.

sonic_service_client/dbus_client.go

@@ -116,7 +116,7 @@ func (c *DbusClient) ApplyPatchYang(patch string) error {
 	busName := c.busNamePrefix + modName
 	busPath := c.busPathPrefix + modName
 	intName := c.intNamePrefix + modName + ".apply_patch_yang"
-	err := DbusApi(busName, busPath, intName, 60, patch)
+	err := DbusApi(busName, busPath, intName, 180, patch)
 	return err
 }
 
@@ -126,7 +126,7 @@ func (c *DbusClient) ApplyPatchDb(patch string) error {
 	busName := c.busNamePrefix + modName
 	busPath := c.busPathPrefix + modName
 	intName := c.intNamePrefix + modName + ".apply_patch_db"
-	err := DbusApi(busName, busPath, intName, 60, patch)
+	err := DbusApi(busName, busPath, intName, 180, patch)
 	return err
 }