use readFileSync for reading pid file

[anas005]

When initialising HAProxy using new HAProxy(), it asynchronously reads the pid file.
So, calling haproxy.reload() after initialising, results in pid as ""(empty string) as the pid file has not yet read.
This PR fixes the issue by using readFileSync for reading pid if there is no callback provided to Orchestrator.prototype.read

[coveralls]

Coverage decreased (-0.2%) to 85.294% when pulling 51dc2c7 on anas005:master into 93d7bf9 on observing:master.

[coveralls]

Coverage decreased (-0.2%) to 85.294% when pulling 51dc2c7 on anas005:master into 93d7bf9 on observing:master.