Remove LOGLEVEL DB since is no longer used (#56)

This PR is part of the following HLD:
Persistent loglevel HLD: sonic-net/SONiC#1041

#### Why I did it
After the Logger tables moved from the LOGLEVEL_DB to the CONFIG_DB and the jinja2_cache was deleted the LOGLEVEL_DB is not in use.
#### How I did it
Removed the LOGLEVEL_DB from the SONiC code

#### How to verify it
All tests were passed

doc/grpc_telemetry.md

@@ -30,7 +30,6 @@ In SONiC, most of the critical network and system data is stored in redisDB. Bas
 |APPL_DB    |  0 |   Application running data |
 |ASIC_DB    |  1 |   ASIC configuration and state data
 |COUNTERS_DB | 2 |   Counter data for port, lag, queue
-|LOGLEVEL_DB | 3 |   Log level control for SONiC modules
 |CONFIG_DB   | 4 |   Source of truth for SONiC configuration
 |FLEX_COUNTER_DB| 5 | For PFC watch dog counters control and other plugin extensions
 |STATE_DB       | 6 | Configuration state for object in CONFIG_DB

proto/sonic.proto

@@ -11,7 +11,6 @@ enum Target {
   APPL_DB         = 0;
   ASIC_DB         = 1;
   COUNTERS_DB     = 2;
-  LOGLEVEL_DB     = 3;
   CONFIG_DB       = 4;
   // PFC_WD_DB shares the the same db number with FLEX_COUNTER_DB
   PFC_WD_DB       = 5;

testdata/database_config.json

@@ -22,11 +22,6 @@
             "separator": ":",
             "instance" : "redis"
         },
-        "LOGLEVEL_DB" : {
-            "id" : 3,
-            "separator": ":",
-            "instance" : "redis"
-        },
         "CONFIG_DB" : {
             "id" : 4,
             "separator": "|",

testdata/database_config_asic0.json

@@ -22,11 +22,6 @@
             "separator": ":",
             "instance" : "redis"
         },
-        "LOGLEVEL_DB" : {
-            "id" : 3,
-            "separator": ":",
-            "instance" : "redis"
-        },
         "CONFIG_DB" : {
             "id" : 4,
             "separator": "|",