Rewrite bmc_command

This helps not fail if /usr/bin/bmc doesn't exist

Fix https://bugzilla.novell.com/show_bug.cgi?id=858207
Merge pull request #69 from vuntz/fix-missing-bmc

Do not fail if /usr/bin/bmc doesn't exist
Drop executable bits on files
Merge pull request #70 from vuntz/no+x

Drop executable bits on files