Add -P option to bootstrap-salt.sh
Add -P option to bootstrap-salt.sh

This option is needed to install pip packages during
Salt bootstrap.

Change-Id: I97d216c02b495a2ca6644399ecfeda25883d2a76
Closes-Bug: #1478216

stackforge/fuel-dev-tools,stackforge/fuel-dev-tools,stackforge/fuel-dev-tools