Change transport type preference

[nkryuchkov]

Did you run make format && make check? Yes

Fixes #157

Changes:

• When calling skywire-cli visor add-tp $PubKey without specifying the transport type explicitly, the visor tries to establish an stcp transport by default and only establish a dmsg transport once that fails.

How to test this PR:

1. Run integration env
2. Run skywire-cli visor add-tp $PubKey without explicitly specifying transport type or run make integration-startup in https://github.com/SkycoinPro/skywire-services/pull/109

[jdknives]

When running in deployment, I get:

[2020-03-10T19:19:08+01:00] DEBUG [tp_manager]: Initializing TP with ID 3c776105-f783-039f-b6c8-e1d43b7f9f9a
[2020-03-10T19:19:08+01:00] INFO [tp_manager]: saved transport: remote(02a2f5c95e2275ed59ad82bcf99adf839b2adb1357f449076f4713f172230254e3) type(stcp) tpID(3c776105-f783-039f-b6c8-e1d43b7f9f9a)
[2020-03-10T19:19:08+01:00] WARN [tp_manager]: Underlying connection is not yet established. Will retry later. error="pk table: entry of 02a2f5c95e2275ed59ad82bcf99adf839b2adb1357f449076f4713f172230254e3 does not exist"
[2020-03-10T19:19:08+01:00] INFO [visor_rpc:CLI]: Request processed. _elapsed="125.37µs" _method="AddTransport" _received="7:19PM" input=&{RemotePK:02a2f5c95e2275ed59ad82bcf99adf839b2adb1357f449076f4713f172230254e3 TpType:stcp Public:true Timeout:0s} output=&{ID:3c776105-f783-039f-b6c8-e1d43b7f9f9a Local:03ac383847b90baaecddcdd2daeb29f49df896399e08db41fc13c81e0228600447 Remote:02a2f5c95e2275ed59ad82bcf99adf839b2adb1357f449076f4713f172230254e3 Type:stcp Log:<nil> IsSetup:false}
[2020-03-10T19:19:08+01:00] INFO [tp:02a2f5]: Serving. remote_pk=02a2f5c95e2275ed59ad82bcf99adf839b2adb1357f449076f4713f172230254e3 tp_id=3c776105-f783-039f-b6c8-e1d43b7f9f9a tp_index=1

I cannot send messages as it reports that there is no transport found for route. Ls-tp returns the transport of type stcp.

[nkryuchkov]

@jdknives The transport manager didn't return an error if the STCP table doesn't have a requested PK. Fixed that behavior and cannot reproduce it anymore. Could you please try again?