test(endpoint): Make Legato endpoint app to read the input

[marktwtn]

Currently, we do not give any input to the Legato endpoint app.
To make sure the endpoint app would work well, the input should be passed to it.

Goal:
Implement the command line interface to pass the input to Legato endpoint app.

[marktwtn]

Although the main goal is to pass the input for testing, we are also considering that we can assign the ENDPOINT_HOST or ENDPOINT_PORT with the implementation.

However, I found it needs some effort:

• The ENDPOINT_HOST is a macro, which is given during the build steps instead of executing steps.
• The macro is used in the endpoint_core.c instead of endpoint.c. But the command line argument passing implementation is on the endpoint.c side.

c.c @splasky .

[marktwtn]

In addition, if we would like to use the endpoint app command line option with the command app, the format would look like this:

$ app runProc endpoint --exe=endpoint -- --help

[splasky]

Although the main goal is to pass the input for testing, we are also considering that we can assign the ENDPOINT_HOST or ENDPOINT_PORT with the implementation.

However, I found it needs some effort:

• The ENDPOINT_HOST is a macro, which is given during the build steps instead of executing steps.
• The macro is used in the endpoint_core.c instead of endpoint.c. But the command line argument passing implementation is on the endpoint.c side.

c.c @splasky .

I think it is better to set the endpoint and host when app start at the beginning. Remove the ENDPOINT_HOST and ENDPOINT_PORT if you can set the host and port at executing steps.