slow network / fota never finishes on CY8CKIT_062S2_43012

[maclobdell]

Describe the bug
While testing CY8CKIT_062S2_43012 with this example, we encountered the following issues:

• Initial network connection fails sometimes
• The network connection is very slow, causing long delay in FOTA download
• Initialization issue with the latest Mbed OS 6.x and Mbed Client

The issues in the last item are being investigated by the Pelion team in a separate ticket.

We believe that the network issues could be independent of the Mbed OS and Client versions.

We pushed changes to the following branch to allow the network to be tested.
https://github.com/ARMmbed/mbed-os-example-pelion/tree/CY8CKIT_062S2_43012

To Reproduce
Steps to reproduce the behavior:

1. get clone https://github.com/ARMmbed/mbed-os-example-pelion/
2. git checkout -B CY8CKIT_062S2_43012 origin/CY8CKIT_062S2_43012
3. Follow the steps in https://developer.pelion.com/docs/device-management/current/connecting/mbed-os.html starting at step 2 under Configuring Device Management Client, including testing the firmware update.

Expected behavior
The firmware should be able to be downloaded in a few minutes. However, on this device it is very slow and it is difficult to tell if it will ever finish.

Logs
none available

Host system (please complete the following information):

• OS: tested on MacOS, but shouldn't matter
• Compiler: Arm Compiler 6
• Compiler version: (latest version of Mbed Studio as of January 2021)
• Mbed CLI version (if used):

Device information:

• Device: CY8CKIT_062S2_43012
• OS: Mbed OS 5.15.x
• Client version: 4.3.0
• Other SW: [attach printout of mbed ls]

Additional context
Add any other context about the problem here.