Update slf4j-api to 1.7.7
Update slf4j-api to 1.7.7

Change-Id: I15bd1aca606400c5f19016be6283e8bafa17b361

opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open