Make LBaaS total_connections cumulative

The total_connections LBaaS data point is presently incorrectly
listed as a gauge. Since the total_connections data point will be an
ever-increasing value (much the same as bytes_in and bytes_out are),
this commit corrects total_connections to also be cumulative.

Change-Id: I60d468a7d24e0a5bdb4c2f680af24397b4c0d77c
Closes-Bug: #1401352
Merge "Make LBaaS total_connections cumulative"