scripts: scripts-library.sh: Use pgrep -f to find the dstat process
scripts: scripts-library.sh: Use pgrep -f to find the dstat process

The dstat process is actually a python script so running 'pgrep dstat'
will not match it

~# pgrep dstat
~# ps aux|grep dstat
root      5322  1.0  0.2  42888  8876 pts/0    S    16:16   0:00 python /usr/bin/dstat -tcmsdn --top-cpu --top-mem --top-bio --nocolor --output dstat.csv 3

However, we can use 'pgrep -f' to search for 'dstat' in the entire
procees string.

~# pgrep -f dstat
5322

Change-Id: I17c181bf957626cc11a1fe6f954e54c8abbfbd93

cfarquhar/openstack-ansible,openstack/openstack-ansible,openstack/openstack-ansible,stackforge/os-ansible-deployment,bunchc/openstack-ansible,cfarquhar/openstack-ansible,stackforge/os-ansible-deployment,bunchc/openstack-ansible