main/grub: prevent harmless LVM related warnings
Whenever grub-probe is run (by grub-mkconfig) and the root filesystem is on LVM then multiple warnings may be displayed:
File descriptor 7 (socket:[24298]) leaked on vgs invocation. Parent PID 12489: /usr/sbin/grub-probe
These warnings are harmless but annoying and may make users think there is an actual problem with their OS. If the environment variable LVM_SUPPRESS_FD_WARNINGS is set then grub-probe will not display these.
This patch sets LVM_SUPPRESS_FD_WARNINGS when "vgs" is called, so preventing these harmless warnings appearing.