Refactor platform in agent for future RHEL support
Add skeleton in agent platform for RHEL support
RHEL network configuration

Change-Id: Ib82330b3bd7bc4736f202992cc0011e21416782b
RHEL dhclient configuration

Change-Id: I08ac8ee54fa7b192ecd436e11a64e44c87549602
Call rescan_scsi_bus.sh with bosh_common's util

Also don't specify full path, because the bits could locate in
different directories in different distributuions.

Change-Id: Iaca86b77d6a103404b797a4cac174cc115d85830
RHEL block device detector

Change-Id: I5568f778258c6f663917d3f7f4075357a2b2764b