Skips the tombstone GC test in Travis for now.
Skips the tombstone GC test in Travis for now.

Related to #3670

vamage/consul,kingland/consul,i0rek/consul,scalp42/consul,42wim/consul,kingland/consul,kingland/consul,vamage/consul,calgaryscientific/consul,42wim/consul,i0rek/consul,scalp42/consul,i0rek/consul,hashicorp/consul,scalp42/consul,calgaryscientific/consul,calgaryscientific/consul,vamage/consul,youhong316/consul,hashicorp/consul,vamage/consul,calgaryscientific/consul,i0rek/consul,vamage/consul,kingland/consul,42wim/consul,42wim/consul,youhong316/consul,hashicorp/consul,youhong316/consul,calgaryscientific/consul,42wim/consul,kingland/consul,youhong316/consul,youhong316/consul,hashicorp/consul,scalp42/consul,scalp42/consul,i0rek/consul