Fix hack_uname() of mlnxofed_ib_install: POSIX compliance

[Darkness4]

The PR is to fix an issue

This is a small fix for the mlnxofed_ib_install script. mlnxofed_ib_install replaces the uname file and runs on a POSIX shell according to the #!/bin/sh shebang. The == operator is undefined in POSIX shells and shourld use -eq.

The modification include

xCAT-server/share/xcat/ib/scripts/Mellanox/mlnxofed_ib_install

[samveen]

@Obihoernchen for your kind attention. The reasoning behind the change is solid, and is a fix for edge cases.