It could be that the visa has:
1. Six months validity to enter Qatar
2. Six additional months to finish all formalities to convert the visa to a resident visa.
So, IF THAT WOULD BE THE CASE, it is within the hands of Employer 1 to cancel the visa so Employer 2 can apply for a new visa. Or just wait until July/August and MAYBE Employer 2 can apply for your new visa.
It could be that the visa has:
1. Six months validity to enter Qatar
2. Six additional months to finish all formalities to convert the visa to a resident visa.
So, IF THAT WOULD BE THE CASE, it is within the hands of Employer 1 to cancel the visa so Employer 2 can apply for a new visa. Or just wait until July/August and MAYBE Employer 2 can apply for your new visa.