do not load rspec task if no rspec available

On production appliances, rspec gem is not installed
This was causing an error like:

```
rake aborted!
NameError: uninitialized constant RSpec
/var/www/miq/vmdb/lib/tasks/spec_evm.rake:10:in block (2 levels) in <top (required)>'
/var/www/miq/vmdb/lib/tasks/spec_evm.rake:2:inblock in '
/var/www/miq/vmdb/lib/tasks/spec_evm.rake:1:in <top (required)>'
/var/www/miq/vmdb/Rakefile:8:in'
/var/www/miq/vmdb/script/rake:15:in <top (required)>'
/var/www/miq/vmdb/script/rails:6:inrequire'
/var/www/miq/vmdb/script/rails:6:in `'
(See full trace by running task with --trace)
```
Merge pull request #726 from kbrock/appliance_no_rspec

do not load rspec task if no rspec available
Add XFS Filesystem Support

The following portions of the XFS code have been tested:
1) Superblocks
2) Allocation Groups
3) Inodes
4) Directories, including:
 * ShortForm Directory Headers and Entries
 * Single Extent Directory Headers and Entries
 * Single Level BTree Directory Headers and Entries

Unused code has been removed.
Additional updates based on Rubocop warnings have been made.
Additional updates based on @Fryguy comments have been made - mostly based on
file naming conventions.
More testing is needed before release including the find test being written
by @roliveri.

@roliveri @Fryguy @chessbyte please review at your convenience.
Add XFS Filesystem Supportdd XFS Filesystem Support

Code to support Smart State Analysis of XFS filesystems has been
added.  The following has been tested successfully:
1) Superblocks
2) Allocation Groups
3) Inodes
4) Directories, including:
5) ShortForm Directory Headers and Entries
6) Single Extent Directory Headers and Entries
7) Multi-block Extent Directory Headers and Entries
8) Single-level BTree Directory Headers and Entries
9) Multi-level BTree Directory Headers and Entries
10) Single and multi-block extent regular files.
11) Symbolic Links

A fleece test on a local filesystem has been run successfully.
Changes due to relevant RuboCop warnings have been added as well
as those in response to review comments.

@chessbyte @Fryguy @roliveri please review as appropriate.