presto-admin package install should not fail if the same package is installed twice

[OluOyedipe]

presto-admin should check if the package is already installed and if so return a message indicating the package is already installed.

[ebuildy]

Dirty fix, comment line in presto_X.py:

class Worker(Script):
    def install(self, env):
        from params import java_home
        Execute('wget --no-check-certificate {0} -O /tmp/{1}'.format(PRESTO_RPM_URL, PRESTO_RPM_NAME))
	#Execute('export JAVA8_HOME={0} && rpm -i /tmp/{1}'.format(java_home, PRESTO_RPM_NAME))
        self.configure(env)