manager: update log level env variables

Use scoped environment variable names
for custom log levels:
DHTLOGLEVEL -> JAMI_LOG_DHT
SIPLOGLEVEL -> JAMI_LOG_SIP
RING_TLS_LOGLEVEL -> JAMI_LOG_TLS

Change-Id: Ic2dc29413382b5072a7aadb9356eb5b19514674d