Need to call communicate() on subprocess objects before calling wait

[jstevens]

zenpack --install was hanging on me when installing certain zenpacks. The code in ZenPackCmd.py was calling p.wait() right after p = subprocess.Popen(...., stdout=subprocess.PIPE,...) The problem is that the output buffer was filling up and the process was hung waiting for the buffer to be read while ZenPackCmd was waiting for the process to finish. A little googling led to this discussion:
http://bugs.python.org/issue1606
Basically we need a p.communicate() call prior to the p.wait() call. This is essential when using stdout/stdin=subprocess.PIPE when any lengthy output could occur. We should probably get in the habit of doing this everywhere we use p.wait() however.

[jstevens]

(In [9370]) fixes #3260

[jstevens]

Reviewed by ecn

[ian]

(In [9420]) * Refs #3260: Backported r9370 into the zenoss-2.2.x branch

[ecn]

cent5 32-bit native rpm build 24