Fix EOF error on stratup visor

[mrpalide]

Did you run make format && make check? Yes

Fixes #1036

Changes:

• add an sleep on initDmsgHTTP process

How to test this PR:

1. Run ./skywire-cli config gen -dirt
2. Change log_level to debug in the config
3. Run ./skywire-visor -c skywire-config.json (Might have to try multiple times)
4. No warning anymore

[ersonp]

getting this error on shutdown

[2021-12-31T11:54:47+05:30] INFO [5/13] [visor:shutdown:router.serve]: Module stopped cleanly. elapsed=12.463759ms
[2021-12-31T11:54:47+05:30] INFO [4/13] [visor:shutdown:dmsg]: Shutting down module...
[2021-12-31T11:54:47+05:30] INFO [dmsgC]: Stopped serving client!
[2021-12-31T11:54:47+05:30] INFO [dmsgC]: Stopped accepting streams. error="session shutdown" session=024716428e6315d954356e9ad72bea32bb2b41aab5a54a9b5cb4313964016e64d8
[2021-12-31T11:54:47+05:30] INFO [dmsgC]: Session closed. error=<nil>
[2021-12-31T11:54:47+05:30] INFO [dmsgC]: All sessions closed.
[2021-12-31T11:54:47+05:30] INFO [transport_manager]: Dmsg client stopped serving. error="dmsg error 200 - local entity closed"
[2021-12-31T11:54:47+05:30] INFO [visor]: Dmsg client stopped serving. error="dmsg error 200 - local entity closed"
[2021-12-31T11:54:47+05:30] DEBUG [dmsgC]: Deleting entry. entry=       version: 0.0.1
        sequence: 0
        registered at: 1640927201629282314
        static public key: 02aa6fc7009d31622705cb3f2feaa8fe0da10c2ae081cf52e7ba7672bf097defad
        signature: 44e2cd8e0d19a63c2152be1b9e31fdb3d0f0b407b82311469ef2d96b983fbe833e329d714be8758df97bfef1850ba850c66ad0b4d6bd9afce4909f1d0a0fd32c00
        entry is registered as client. Related info: 
                delegated servers: 
                        024716428e6315d954356e9ad72bea32bb2b41aab5a54a9b5cb4313964016e64d8


[2021-12-31T11:54:48+05:30] ERROR [dmsgC:disc]: endpoint="dmsg://03cd2336e5de74bdab2bbdb44b06b0c8c713a5ee9029615f5526f8c99a6afe87b8:80/dmsg-discovery/entry" resp_body="entry validation error: advertised entry has outdated timestamp" resp_status=422
[2021-12-31T11:54:48+05:30] WARN [4/13] [visor:shutdown:dmsg]: Module stopped with unexpected result. elapsed=335.224467ms error="entry validation error: advertised entry has outdated timestamp"
[2021-12-31T11:54:48+05:30] INFO [3/13] [visor:shutdown:dmsg_http]: Shutting down module...
[2021-12-31T11:54:48+05:30] INFO [dmsg_http:dmsgDC]: Stopped serving client!
[2021-12-31T11:54:48+05:30] INFO [dmsg_http:dmsgDC]: Session closed. error=<nil>
[2021-12-31T11:54:48+05:30] INFO [dmsg_http:dmsgDC]: Stopped accepting streams. error="session shutdown" session=024716428e6315d954356e9ad72bea32bb2b41aab5a54a9b5cb4313964016e64d8
[2021-12-31T11:54:48+05:30] INFO [dmsg_http:dmsgDC]: All sessions closed.