Cross-platform udevadm_settle

RHEL doens't have /sbin/udevadm. Call /sbin/udevsettle instead.
Use native method instead of shelling out
Fix typo in comment
Use df's POSIX output format

so that a mount point doesn't go to multiple lines
Use sys-filesystem instead of parsing df which might not be portable and it looks better
Remove commented out log line
Prefer Bosh::Exec when shelling out
Fix sys-filesystem version
Return string for backward compatiblity
Fix test for string values
(nitpicking) Remove rogue whitespace
Fix bosh_agent path in MCF agent startup script.
Update gemlock
Update gemlock
Fix bug if statement(always true)

The if statement in platform/ubuntu/password.rb is always true.
Fix bosh micro apply
Director and Agents should always use same bucket_name
consolidate 3 scripts for the 2 stemcell builds to 1 script
Bundle update to include JSON security patches
Update LICENSE and NOTICE for bat-release