Use jemalloc 2.2.5 by default
Use jemalloc 2.2.5 by default

jemalloc 3.6.0 rarely causes segmentation fault on some environment.
So jemalloc software switches default version to 2.2.5.
jemalloc dev branch seems to fix this problem.
We will use newest version after released new version.

iantalarico/google-fluentd,treasure-data/omnibus-td-agent,GoogleCloudPlatform/google-fluentd,iantalarico/google-fluentd,GoogleCloudPlatform/google-fluentd,GoogleCloudPlatform/google-fluentd,treasure-data/omnibus-td-agent,treasure-data/omnibus-td-agent,iantalarico/google-fluentd